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/roles/cell-pm.md

@@ -149,9 +149,9 @@ Each finding is inserted onto the task's revision-findings ledger (`origin=pm`)
 ## Monitoring Your Cell
 
 ```python
-triage()                       # surfaces tasks waiting on you
-roboco_git_status(...)          # workspace state
-roboco_git_log(...)             # cell branch history
+triage()  # surfaces tasks waiting on you
+roboco_git_status(...)  # workspace state
+roboco_git_log(...)  # cell branch history
 note(text="...", scope="reflect")  # journal observations
 ```
 
@@ -159,12 +159,20 @@ note(text="...", scope="reflect")  # journal observations
 
 ```python
 # Cross-cell coordination
-dm(recipient="fe-pm", text="Need to align on shared schema; task X.",
-   task_id="...", skill="api_design")
+dm(
+    recipient="fe-pm",
+    text="Need to align on shared schema; task X.",
+    task_id="...",
+    skill="api_design",
+)
 
 # Ack-required notification (PMs / Board only)
-notify(target="be-dev-1", text="Please prioritise task X by EOD.",
-       priority="high", task_id="...")
+notify(
+    target="be-dev-1",
+    text="Please prioritise task X by EOD.",
+    priority="high",
+    task_id="...",
+)
 ```
 
 ## Assembling + Submitting Finished Work
@@ -206,7 +214,9 @@ Use `escalate_up(task_id, reason)` when:
 - A non-cell agent is blocking you
 
 ```python
-escalate_up(task_id="<task>",
-            reason="Frontend cell needs the new auth endpoint we own; "
-                   "they're blocked. Want to confirm priority swap.")
+escalate_up(
+    task_id="<task>",
+    reason="Frontend cell needs the new auth endpoint we own; "
+    "they're blocked. Want to confirm priority swap.",
+)
 ```