feat(task-board): redesign the card dialog with autosave, human keys and short links

[rafavalls]

What is this contribution about?

Adds a per-org, human-readable key to each task board card (e.g. DECO-01), derived from a new key_seq column assigned at create time (with retry on raced inserts) and exposed via packages/shared/task-key.ts. Adds a shareable short link route (/$org/t/DECO-01) that resolves the key to a card and forwards to the board's deep link. Reworks the task dialog header to show the new key row, and fixes list-continuation handling in the markdown editor.

How did you verify your code works?

Added unit tests for task-key.ts (prefix derivation, key formatting, term parsing) and for the markdown editor's unwrap-list-continuations. Added a Postgres integration test (task-board-key-seq.integration.test.ts) covering key_seq assignment and the raced-insert retry path. Updated existing task-board schema/reaction/update/filters/config tests for the new keySeq field.

Screenshots/Demonstration

N/A — no screenshots captured in this session; the task dialog header now renders the card's DECO-01-style key.

How to Test

1. Run bun run --cwd=apps/api migrate to apply migration 172-task-board-item-key-seq.
2. Create a new task board card and confirm it shows a DECO-01-style key in the dialog header.
3. Visit /$org/t/<key> and confirm it redirects to the board with that card opened.

Migration Notes

Requires running the new Kysely migration apps/api/migrations/172-task-board-item-key-seq.ts, which adds and backfills the key_seq column on task_board_items.

Review Checklist

• PR title is clear and descriptive
• Changes are tested and working
• Documentation is updated (if needed)
• No breaking changes

---

Summary by cubic

Redesigns the task dialog with autosave and human task keys plus short links. Old behavior: a Save button and each autosave spammed the timeline; new behavior: a 2s autosave with blur flush and server‑side coalescing that merges repeated title/description edits by the same actor within 10 minutes.

Assigns a per‑org sequence (key_seq) at create under a per‑org advisory lock, with a unique (organization_id, key_seq) index to prevent duplicates. Exposes keySeq and renders keys like DECO-01. Adds /$org/t/DECO-01 short links that resolve by human key or raw id and forward to the board; the router preserves a task param through the landing redirect; board search matches keys (DECO-07, deco-7, or 7). Reworks the dialog: moves actions into a menu (clone, archive, delete, new chat, auto‑fix/rerun), adds copy/share for the key, collapses long descriptions and folds long activity runs, shows PRs as read‑only rows, and clips the description only while folded so image controls stay clickable. Normalizes wrapped list items before parsing so the editor does not drop text. Tests cover Postgres key allocation under lock (forced interleaving) and activity coalescing, key helpers and resolvers, and markdown normalization; e2e closes the dialog to flush autosave.

Rollout

• Run migration 172-task-board-item-key-seq to add/backfill key_seq and create the unique index.
• Verify a new card shows a DECO-01‑style key and that visiting /$org/t/<key or id> opens that card on the board.

^{Written for commit 68339c3. Summary will update on new commits.}