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>

tests/unit/services/test_board_program_engine.py

@@ -471,6 +471,23 @@ async def test_prior_cycle_context_renders_rejections_with_reasons(
     assert "item-2 — too risky" in context
 
 
+def test_learn_ref_names_the_item_not_its_per_cycle_index() -> None:
+    """The ref reaches the next cycle's prompt, so it must say WHAT was
+    decided — ``item-1`` means something different in every cycle."""
+    assert bp_module.learn_ref({"id": "item-1", "title": "Fix the CLA gate"}) == (
+        "Fix the CLA gate"
+    )
+    # Scales items name the live task they mutate instead of a draft title.
+    assert bp_module.learn_ref(
+        {"id": "item-0", "target_task_title": "Panel UX wave"}
+    ) == ("Panel UX wave")
+    # A title-less item degrades to the old behaviour rather than an empty ref.
+    assert bp_module.learn_ref({"id": "item-2"}) == "item-2"
+    assert bp_module.learn_ref({"id": "item-3", "title": "   "}) == "item-3"
+    cap = 80
+    assert len(bp_module.learn_ref({"id": "item-4", "title": "x" * 200})) == cap
+
+
 def test_originators_cover_exactly_the_registry() -> None:
     assert set(bp_module._ORIGINATORS) == set(PROGRAMS)