fix: keep task writer transitions committable

.codearbiter/specs/commit-gate-board-sync.md

@@ -35,7 +35,8 @@ commit-gate expect and stage the flip, and to add a backstop sweep for any flip
 ## Atomicity rules (from ADR-0008, for reference)
 
 - **done-flip** `[~]`→`[x]` rides the **completing** commit; reverts on abandonment (self-correcting).
-- **start-flip** `[ ]`→`[~]` rides the **first** work commit; reverts on abandonment.
+- **start-flip** `[ ]`→`[~]` rides the **first** work commit; it may also mint the
+  task's single valid dotted ID at pick-up, and reverts on abandonment.
 - **raise-new** add `[ ]` rides the work commit (harvest pre-commit), **contingent default**; a
   follow-up that must survive abandonment is filed as a **GitHub issue**, not a board-only side commit.
 
@@ -48,11 +49,15 @@ pattern already used by `test_ux_conversion.py`.
    change is one entry flipping `[~]`+started-date → `[x]`+done-date, the `_taskboardlib` transition
    classifier returns *is-transition*.
 2. **Classifier — start-flip and add positive.** It returns *is-transition* for (a) a clean start-flip
-   `[ ]`→`[~]` with a stamped started-date and no other change, and (b) an appended queued
-   `- [ ] <desc>` entry with no other change.
+   `[ ]`→`[~]` with a stamped started-date and no other change except the optional single valid
+   dotted ID minted for an ID-less task at pick-up, and (b) an appended queued `- [ ] <desc>` entry
+   with no other change. When the writer's requested section is absent, (b) may also append exactly
+   that one level-two section heading immediately before the queued entry.
 3. **Classifier — arbitrary-edit negative.** It returns *not-transition* when the diff includes any
-   change beyond a state-cell flip, its stamped date, or a single appended queued entry — e.g. a
-   reworded description, a deleted entry, or an edit to a non-target line.
+   change beyond a state-cell flip, its stamped date, the start-flip's optional minted ID, or a
+   single appended queued entry and its necessary new section heading — e.g. a reworded
+   description, a deleted entry, free-form content beside a new section, or an edit to a non-target
+   line.
 4. **Phase 6 exemption (prose).** commit-gate `SKILL.md` Phase 6 states that an `open-tasks.md` edit the
    classifier marks *is-transition* is retained (not flagged as scope creep), while any other board edit
    still flags — and names the classifier as the test.

.codearbiter/specs/task-board-lifecycle.md

@@ -112,7 +112,9 @@ stage-blocking). MVP ships without any of them.
 
 - **D-1 — Transition writer surface.** New `/ca:task` (add/start/done) vs. extend
   `/ca:standup`/`/ca:status` vs. manual edit. MVP ships with the schema + counters +
-  nudge; transitions are hand-edited until decided. Gates AC-11.
+  nudge; transitions are hand-edited until decided. Gates AC-11. **Resolved
+  post-MVP:** `/ca:task` now enforces `[ ]`→`[~]`→`[x]`; `done` rejects a queued task
+  and tells the caller to `start` it first (see `task-writer-harvest.md`).
 - **D-2 — Archival sweep owner + cutoff.** Which command runs the confirmed
   done→`done-tasks.md` sweep, and the "long-settled" age (done >N days). Archival is
   post-MVP.

.codearbiter/specs/task-writer-harvest.md

@@ -32,12 +32,17 @@ its origin, under confirmation.
     section="## In-flight") -> str` — append a queued entry. ID-LESS by default:
     `- [ ] <desc>  (from <origin>)`. When `group`+`type` are given, mints
     `<group>.<type>.<NNNN>` via `next_seq`. Result is lint-clean; creates `section`
-    if absent.
+    if absent. The description must be nonblank and single-line; the section must
+    be one canonical level-two heading; origin and boundary values must be
+    single-line. Invalid input returns the original text unchanged.
   - `set_state(text, target, state, today, *, assign=None) -> str` — flip a task's
-    marker (`target` = a dotted id, or the title of an ID-less item). `in_progress`
-    ALWAYS stamps `(started <today>)`; `done` stamps `(done <today>)`. When `assign`
-    = `group.type` and the target is ID-less, mints its dotted ID at the same time
-    (the "ID on pick-up" path).
+    marker (`target` = a dotted id, or the title of an ID-less item). Valid target
+    states are only `in_progress` and `done`; `queued` remains a parse/add state,
+    never a transition target. `in_progress` accepts a queued task and ALWAYS stamps
+    `(started <today>)`; `done` accepts an in-progress task and stamps `(done
+    <today>)`. A direct queued-to-done transition is rejected unchanged. When
+    `assign` = `group.type` and the target is ID-less, mints its dotted ID at the
+    same time (the "ID on pick-up" path).
   - `already_promoted(text, origin) -> bool` — True iff an open (non-done) entry
     carries `(from <origin>)`.
 - **Three pure extractors** (artifact text + origin → candidate list):
@@ -87,15 +92,21 @@ suite; reuses existing vocab (`NEEDS-TRIAGE`, DEFERRABLE, `[CONFIRM-NN]`).
    desc="X", origin="checkpoint-2026-06-13#H-2")` appends
    `- [ ] X  (from checkpoint-2026-06-13#H-2)` under `## In-flight`; `count_in_flight`
    +1 and `lint_board` clean. Given `group="v2", type="followup"` it instead appends
-   `- [ ] v2.followup.0001 - X  (from …)`.
-3. **AC-03 — start/done transitions are dated.** `set_state(board, "v2.api.0001",
-   "in_progress", date(2026,6,21))` flips `[ ]`→`[~]` and adds `(started 2026-06-21)`;
-   `"done"` flips to `[x]` and adds `(done 2026-06-21)`. A re-`done` is a safe no-op.
+   `- [ ] v2.followup.0001 - X  (from …)`. Blank or multiline descriptions,
+   non-heading/multiline sections, multiline origins, and multiline boundary values
+   are rejected unchanged; the CLI reports the invalid field before writing.
+3. **AC-03 — start/done transitions are ordered and dated.** `set_state(board,
+   "v2.api.0001", "in_progress", date(2026,6,21))` flips `[ ]`→`[~]` and adds
+   `(started 2026-06-21)`; applying `"done"` to that in-progress result flips
+   `[~]`→`[x]` and adds `(done 2026-06-21)`. Applying `done` directly to a queued
+   task is rejected unchanged, and the writer tells the caller to `start` it first.
+   A re-`done` is a safe no-op.
 4. **AC-04 — start of an ID-less item mints + dates** (the pick-up path, D-1 hole
    closed): `set_state(board, "<title>", "in_progress", date(2026,6,21),
    assign="v2.api")` assigns the next `v2.api.NNNN` dotted ID AND stamps
    `(started 2026-06-21)`; `undated_in_progress` on the result is empty and the item
-   validates.
+   validates. A malformed `assign`/`--as` namespace (extra or empty component,
+   whitespace, or a character outside the ID grammar) is rejected before write.
 5. **AC-05 — set_state on a missing target** returns the text unchanged and signals
    not-found (no silent partial write, no raise).
 6. **AC-06 — dedup by origin.** `already_promoted(board, origin)` is True once an open