Board Program LEARN context, ruff 0.16, and verb-rejection observability (#700)

* fix(board): LEARN decisions name the item, not its per-cycle index

A cycle's reject reasons are rendered into the NEXT cycle's exploration
prompt, but the ref recorded alongside each reason was the item's stored
id (item-0/item-1) — a per-cycle index that means something different
every cycle and appears nowhere the explorer can resolve. The reason
survived the loop; what it was about did not.

Record the item's title instead, via a shared learn_ref() helper (falls
back to the id when title-less, and reads target_task_title for Scales,
whose items name the live task they mutate).

* chore(lint): satisfy ruff 0.16 — keyword-only signatures and markdown formatting

The dev toolchain resolved ruff 0.16.0, which stabilises PLR0917 (too many
positional arguments) and formats python code blocks inside markdown. Both
fired repo-wide and neither had anything to do with the code they flagged.

- 36 signatures gain a `*` so their tail arguments are keyword-only, and
  the 104 call sites that passed them positionally are converted. mypy was
  the safety net for the static ones; the full suite caught nine more that
  only bind at runtime (the MCP tool functions, whose real callers already
  pass named JSON arguments).
- 28 markdown files reformatted by 0.16's code-block formatter.
- One RUF036 (`None` mid-union) autofixed in the GitLab provider.

* fix(gateway): log the reason when a verb rejects

A rejected envelope rides an HTTP 200, its body is never logged, and there
is no trace table — so in the access log a verb an agent could not satisfy
looks identical to one that worked. On 2026-07-25 four Board Programs
(Periscope, Sentinel, Scales, Barfly) each POSTed their propose verb three
or four times, persisted nothing, and left their exploration tasks PENDING;
the reason was unrecoverable afterwards, from the logs or from the agents'
own transcripts.

Log error/message/remediate/missing plus the calling agent at
envelope_to_response — the one chokepoint every v1 flow and do route
returns through. Success envelopes stay silent.

---------

Co-authored-by: Renn F <rennf93@users.noreply.github.com>

docs/rag/workflows/qa-review.md

@@ -27,10 +27,12 @@ roboco_git_log(branch="<dev's branch>")
 # Frontend: pnpm test && pnpm lint && pnpm typecheck
 
 # 5. Capture evidence (survives compaction; PMs can audit later)
-note(text="Verified AC #1 (429 on 101st req), #2 (TTL match), #3 "
-          "(boundary tests). pytest 1635 passed; ruff clean; mypy clean.",
-     scope="evidence",
-     task_id="<task>")
+note(
+    text="Verified AC #1 (429 on 101st req), #2 (TTL match), #3 "
+    "(boundary tests). pytest 1635 passed; ruff clean; mypy clean.",
+    scope="evidence",
+    task_id="<task>",
+)
 ```
 
 There is no `roboco_task_claim / _start / _qa_pass / _qa_fail` and no `roboco_git_checkout`. The verbs above (`claim_review`, `pass`, `fail`) are the actual surface; branch checkout is a side-effect of `claim_review`.