feat(web): simplify sidebar drag destination cues

[juliusmarminge]

Dragging between sections repeats the move instruction on the boundary while the dragged thread still shows its old pin. This optional follow-up to #9731 puts that feedback on the thread: → Pinned, → Active, or → Settled appears when crossing sections. The usual pin, status, and hover actions hide during dragging; reordering within a section shows no destination badge. Boundaries keep their section names and highlight.

The sortable layout, drop behavior, and movement animations are unchanged. This affects the shared web/desktop sidebar, including compact rows dragged out of Snoozed or Settled. It can be accepted or closed independently of the parent PR.

Verified with 203 focused sidebar tests, web typecheck, targeted lint, and an independent code review. React Doctor reported only existing sidebar complexity warnings. The recordings exercise pinning and unpinning on matching fixtures; the dark screenshots cover a compact Settled row moving toward Active.

Before and after — pinned thread moving into Active

Before — parent	After — experiment

Before recording — pickup, unpin, then pin again:

https://gh-file-drop-api-prod-mi5fy3sowv63ufte.pinglabs.workers.dev/f/ff678fdac0988ddd/before-drag-destination-cues.mp4

After recording — the same sequence with the destination cue on the row:

https://gh-file-drop-api-prod-mi5fy3sowv63ufte.pinglabs.workers.dev/f/4fd7ab881f826aa5/after-drag-destination-cues.mp4

Compact row in dark mode — Settled to Active

Before — parent	After — experiment

Evidence compares parent d2c3f461c5 with this PR at 896abc27b0. Screenshots and recordings use the same sidebar fixtures and viewport.

Prepared with Codex.

Note

Simplify sidebar drag destination cues and add accessible Move to badge

• Removes contextual hint text from SidebarDragBoundary, SidebarSectionHeader, and SidebarThreadRow during drag operations
• Adds an accessible hidden "Move to" prefix to the destination badge shown only on the actively dragged row when it crosses into a different section (pinned, active, or settled)
• Hides pin indicators, status, and hover-action slots during a drag, replacing them with the destination badge in both slim and card layouts
• Snoozed is no longer offered as a drag destination; same-section reordering shows no badge
• Updates thread-sidebar.md to reflect the new drag-and-drop behavior

^{Macroscope summarized 896abc2.}

---

Note

Low Risk
Presentation-only changes to sidebar drag UI and copy; DnD drop logic and server commands are untouched.

Overview
This PR simplifies sidebar drag feedback so move instructions live on the dragged row instead of repeating on section boundaries.

Section chrome no longer shows contextual hints (Drop to pin, Drop to settle, etc.). SidebarDragBoundary and SidebarSectionHeader only display section names and highlight when they are drop targets. Empty Active and Settled placeholders use those section names instead of drop instructions.

While dragging across sections, the active row shows a → Pinned / Active / Settled badge (with a screen-reader Move to prefix). The badge appears only when the hover target section differs from the source and is not Snoozed; same-section reordering shows no destination. The pin control and the usual status/hover slots are suppressed for the duration of the drag so they do not compete with the badge.

Drop planning and sortable behavior are unchanged; user docs in thread-sidebar.md describe the new cues.

^{Reviewed by Cursor Bugbot for commit 896abc2. Bugbot is set up for automated code reviews on this repo. Configure here.}

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

ℹ️ No successful main baseline artifact is available yet. This run establishes the initial measurement.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	—	13.8 KiB	—	15.1 KiB	✅
Codex	Thread snapshot wire	—	7.0 KiB	—	7.3 KiB	✅
Codex	Live turn WebSocket wire	—	6.7 KiB	—	7.8 KiB	✅
Codex	Live turn WebSocket decoded	—	58.5 KiB	—	66.4 KiB	✅
Codex	Live turn messages	—	10	—	21	✅
Claude	Total thread wire	—	13.8 KiB	—	15.1 KiB	✅
Claude	Thread snapshot wire	—	7.0 KiB	—	7.3 KiB	✅
Claude	Live turn WebSocket wire	—	6.7 KiB	—	7.8 KiB	✅
Claude	Live turn WebSocket decoded	—	59.3 KiB	—	66.4 KiB	✅
Claude	Live turn messages	—	10	—	21	✅

Baseline: unavailable · PR result: 896abc2 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 113.9 KiB
• Claude decoded thread snapshot: 114.5 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

[macroscopeapp]

Approvability

Verdict: Approved at 896abc2

Macroscope's review found this PR approvable — This is a contained sidebar UX refinement that changes only drag-time destination cues and temporarily hides existing row controls; the underlying drag targets, drop actions, and persistence remain unchanged. Documentation is updated alongside the isolated UI change, with no schema, infrastructure, security, billing, or static-analysis impact.

^{You can add or adjust custom eligibility rules. Learn more.}

Dismissing prior approval to re-evaluate 896abc2