[backnotprop]

Rebuilds the image-attachment half of #73 (by @MaterAnime, credited as co-author) on current main. The multi-reply half of #73 already shipped, so it is not included.

What it does

• I (attach-image) opens a one-line path prompt for the selected note in the notes rail, or the selected block's note in the document. Typed, pasted (bracketed paste) and dropped paths work: quotes, ~, file://, shell-escaped spaces, and paths relative to the document's folder. Missing files and non-image extensions (png, jpg, jpeg, gif, webp, bmp, svg) are refused in the status line with the prompt left open; a path already on the note is ignored.

• D (remove-image) removes the last image added. Both keys are rebindable under [keys], unused elsewhere in the default keymap, and shown in the footer hints from the keymap.

• Paths are stored under the annotation's plannotator_tui.images, omitted when empty, so older records load unchanged and Workspaces' attachments (https URLs only) is untouched.

• Adding or removing an image makes a sent note pending again.

• Feedback and --export list each image under its note:

  ## Annotation 1 (line 3)
  Comment on: "Ship the login page."
  > check spacing
  Image: /Users/me/shots/screen shot.png
  

• The rail bubble title shows · 1 image / · N images; the feedback archive's counts.images is filled.

• Images stay local references: nothing is copied or uploaded.

Decision 16 in docs/decisions.md records the storage and output choices; README key tables are updated.

Tests: schema round trip and old-record compatibility, export line format, path parsing (quotes, relative, file://, escaped spaces, missing, wrong extension, directories), and an app flow test (attach from document and rail, duplicate, send, archive count, reopen, remove). cargo fmt --check, cargo clippy --workspace --all-targets -D warnings, and cargo test --workspace --all-targets pass locally; also smoke-tested in tmux.

Refs #73