Add drag-and-drop uploads to the rich editor

docs/DEMO_LIBRARY.md

@@ -64,7 +64,8 @@ shipped types, including Scratchpad, PRD, Test Plan, and Handoff.
 | discussion-margins | Crowded prose discussions, multiple participants, resolved visibility, and slide navigation/scrolling; avatars identify starters, not unread activity |
 | reading-specimen | A realistic design doc for judging reading in both modes: prose, headings, lists, tasks, quote, table, footnote, image, SQL/Ruby/diff/YAML code, a long scrolling line, flowchart and sequence diagrams, plus open, agent-answered, resolved, diagram-node, table-cell, and general discussions |
 | document-title | One editable title; autosave keeps the URL stable until Done; title boundaries and empty-title behavior |
-| image-resizing | Resize and restore image widths, wrap prose from the top, Shift+Enter beside, Enter below |
+| image-resizing | Drop or paste files to upload and embed; duplicate drops reuse files; resize images, wrap prose, Shift+Enter beside, Enter below |
+| file-uploads | Drop the same image or file again: one attachment and stored copy, multiple embeds; renamed copies, Dual, and Undo |
 | callout-gallery | `> [!SUMMARY]`, `[!NOTE]`, `[!TIP]`, `[!IMPORTANT]`, `[!WARNING]`, and `[!CAUTION]` callouts, a custom label, nested list and code, plain and escaped quotes, and both deck themes; comment inside a callout, or edit one in Editor and check Raw |
 | math-gallery | KaTeX math: inline, display, and fenced formulas, math in lists and tables, a six-row slide equation, dollar amounts that stay text, and invalid math shown as source; comment on the text around a formula |
 

docs/human-document-editor.md

@@ -104,6 +104,12 @@ Images have a bottom-right resize handle that appears on hover or keyboard focus
 
 Images pasted from other apps start at their natural size, capped by the document width. A copied thumbnail's display width is ignored. Copying an image within Coplan's rich editor preserves its intentional resize. Existing saved widths and widths written in Raw Markdown stay unchanged.
 
+Drop image or file uploads into the rich Editor or the rich pane in Dual. Images appear inline; other supported files become download links. Clipboard image files upload too. Upload markers follow their insertion points through continued typing and live updates, without entering saved Markdown. Uploads use the plan's existing type and 25 MB size limits. A new document is created before its first upload. Done and navigation wait for pending uploads before saving. Partial failures preserve accepted files and show per-file errors. Drop failed files again to retry. Undo removes an embed while keeping the file in Attachments; deleting its drop point during upload leaves the file available there too.
+
+Identical uploaded contents reuse an existing attachment within the same document, preserving its original filename and uploader. Every drop still inserts an embed at that location. The notice distinguishes uploads from reuse. Different contents, even with the same filename, stay separate. Concurrent identical uploads converge on one attachment and stored blob; reuse does not log another attachment-added event. Existing duplicate attachments are left intact so their saved links continue working.
+
+Upload errors stay visible until dismissed, including after another file succeeds. Done and navigation keep the editor open while these errors are unacknowledged. Dismiss the notice before leaving; your writing and accepted files remain saved.
+
 Text after a paragraph's leading image wraps beside it from the top when there is room, in both editing and reading views. Enter starts a paragraph below the image; Shift+Enter keeps a line break beside it. In Raw Markdown, a blank line starts the paragraph below. Images inside a sentence remain inline.
 
 **+ → Embed** adds a self-closing iframe block with URL, title, width,

engine/app/assets/stylesheets/coplan/document-editor.css

@@ -184,3 +184,54 @@ html[data-theme="light"] .document-editor select, html[data-theme="light"] .docu
   .document-editor[data-mode="dual"] .document-editor__raw { padding-right: 0; padding-bottom: 24px; border-right: 0; border-bottom: 1px solid var(--color-border); }
   .document-editor[data-mode="dual"] .ProseMirror { min-height: 200px; }
 }
+.document-editor .ProseMirror.is-file-drop-target {
+  outline: 2px solid var(--color-primary);
+  outline-offset: 6px;
+  background: var(--color-interaction-hover-bg);
+}
+
+.document-editor__upload-placeholder {
+  display: inline-flex;
+  align-items: center;
+  gap: 0.5rem;
+  max-width: 100%;
+  padding: 0.35rem 0.65rem;
+  border: 1px solid var(--color-primary);
+  border-radius: 0.5rem;
+  color: var(--color-primary);
+  background: var(--color-interaction-hover-bg);
+  font-size: 0.85rem;
+  overflow-wrap: anywhere;
+}
+
+.document-editor__upload-placeholder::before {
+  content: "";
+  width: 0.8rem;
+  height: 0.8rem;
+  flex-shrink: 0;
+  border: 2px solid currentColor;
+  border-right-color: transparent;
+  border-radius: 50%;
+  animation: editor-upload-spin 0.8s linear infinite;
+}
+
+.document-editor__upload-notice {
+  position: fixed;
+  inset: auto 1rem 1rem auto;
+  z-index: 120;
+  max-width: min(28rem, calc(100vw - 2rem));
+  margin: 0;
+  padding: 0.75rem 1rem;
+  border: 1px solid currentColor;
+  border-radius: 0.65rem;
+  background: var(--color-surface);
+  color: var(--color-primary);
+  font-size: 0.85rem;
+}
+
+.document-editor__upload-notice[data-error="true"] { color: var(--color-danger); }
+.document-editor__upload-notice button:not([hidden]) { display: block; margin-top: 0.5rem; }
+@keyframes editor-upload-spin { to { transform: rotate(360deg); } }
+@media (prefers-reduced-motion: reduce) {
+  .document-editor__upload-placeholder::before { animation: none; }
+}

engine/app/controllers/coplan/api/v1/attachments_controller.rb

@@ -37,7 +37,7 @@ def create
           )
 
           if result.success?
-            render json: attachment_json(result.attachment), status: :created
+            render json: attachment_json(result.attachment).merge(reused: result.reused?), status: :created
           else
             render json: { error: result.error }, status: :unprocessable_content
           end

engine/app/controllers/coplan/attachments_controller.rb

@@ -10,22 +10,40 @@ def create
       files = Array(params[:files]).reject(&:blank?)
       if files.empty?
         return respond_to do |format|
+          format.json { render json: { attachments: [], errors: [ "Choose at least one file to upload." ] }, status: :unprocessable_content }
           format.turbo_stream { render turbo_stream: toast_stream("Choose at least one file to upload.", "alert") }
           format.html { redirect_to helpers.plan_browse_path(@plan, anchor: "footnote-attachments"), alert: "Choose at least one file to upload." }
         end
       end
 
       errors = []
+      attachments = []
       files.each do |file|
         result = Plans::AddAttachment.call(plan: @plan, file: file, user: current_user)
-        errors << "#{file.original_filename}: #{result.error}" unless result.success?
+        if result.success?
+          blob = result.attachment.blob
+          url = main_app.rails_blob_path(blob, only_path: true)
+          attachments << { id: result.attachment.id, filename: blob.filename.to_s,
+            content_type: blob.content_type, url: url, reused: result.reused?,
+            download_url: main_app.rails_blob_path(blob, disposition: :attachment, only_path: true) }
+        else
+          errors << "#{file.original_filename}: #{result.error}"
+        end
       end
 
-      uploaded = files.size - errors.size
-      notice = "#{uploaded} #{"file".pluralize(uploaded)} uploaded." if uploaded.positive?
+      uploaded = attachments.count { |attachment| !attachment[:reused] }
+      reused = attachments.size - uploaded
+      notice = []
+      notice << "#{uploaded} #{"file".pluralize(uploaded)} uploaded." if uploaded.positive?
+      notice << "#{reused} existing #{"file".pluralize(reused)} reused." if reused.positive?
+      notice = notice.join(" ").presence
       alert = errors.join(" ") if errors.any?
 
       respond_to do |format|
+        format.json do
+          render json: { attachments: attachments, errors: errors, streams: attachment_update_streams.map(&:to_s).join },
+            status: attachments.any? ? :created : :unprocessable_content
+        end
         # In-place: swap the attachments section where it stands and toast —
         # never bounce the reader to the top of the plan they're in.
         format.turbo_stream { render_attachments_update(notice: notice, alert: alert) }
@@ -72,8 +90,15 @@ def set_plan
     # message — the whole point is that the reader's scroll position never
     # moves.
     def render_attachments_update(notice: nil, alert: nil)
+      streams = attachment_update_streams
+      streams << toast_stream(notice, "notice") if notice
+      streams << toast_stream(alert, "alert") if alert
+      render turbo_stream: streams
+    end
+
+    def attachment_update_streams
       attachments = @plan.attachments_attachments.includes(:blob).order(created_at: :desc)
-      streams = [
+      [
         turbo_stream.replace("plan-attachments",
           partial: "coplan/plans/attachments",
           locals: { plan: @plan, attachments: attachments }),
@@ -82,9 +107,6 @@ def render_attachments_update(notice: nil, alert: nil)
         count_stream("attachments-count", attachments.size),
         count_stream("nav-attachments-count", attachments.size)
       ]
-      streams << toast_stream(notice, "notice") if notice
-      streams << toast_stream(alert, "alert") if alert
-      render turbo_stream: streams
     end
 
     def count_stream(id, count)

engine/app/controllers/coplan/plans_controller.rb

@@ -239,7 +239,8 @@ def create
       edit_url = helpers.plan_browse_path(plan, edit: "continue")
       render json: editor_snapshot.merge(edit_url: edit_url, inline_after_create: true, id: plan.id,
         subscription_html: helpers.turbo_stream_from(plan),
-        update_url: update_content_plan_path(plan), state_url: editor_state_plan_path(plan), lease_url: editor_lease_plan_path(plan))
+        update_url: update_content_plan_path(plan), state_url: editor_state_plan_path(plan), lease_url: editor_lease_plan_path(plan),
+        attachments_url: plan_attachments_path(plan))
     rescue Plans::CreateHumanDraft::InvalidKey => error
       render json: { error: error.message }, status: :unprocessable_content
     rescue Plans::CreateHumanDraft::PlacementFailed => error