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/gateway/test_dev_steps_gate.py

@@ -115,7 +115,7 @@ async def test_dev_fresh_claim_without_steps_is_rejected() -> None:
     task_id = uuid4()
     c = Choreographer(_make_deps(task=_dev_task_svc(task_id)))
 
-    env = await c.i_will_work_on(dev_id, task_id, plan="do the thing")
+    env = await c.i_will_work_on(agent_id=dev_id, task_id=task_id, plan="do the thing")
     body = env.as_dict()
     assert body["error"] == "incomplete_input", body
     assert "steps" in (body.get("missing") or []), body
@@ -128,8 +128,8 @@ async def test_dev_thin_step_description_is_rejected() -> None:
     c = Choreographer(_make_deps(task=_dev_task_svc(task_id)))
 
     env = await c.i_will_work_on(
-        dev_id,
-        task_id,
+        agent_id=dev_id,
+        task_id=task_id,
         plan="do the thing",
         steps=[{"title": "Edit README", "description": "edit it"}],
     )
@@ -162,7 +162,9 @@ async def test_dev_with_substantive_steps_passes_gate_and_persists_checklist() -
         {"title": "Edit README", "description": _GOOD_STEP_DESC},
         {"title": "Commit + open PR", "description": _GOOD_STEP_DESC},
     ]
-    env = await c.i_will_work_on(dev_id, task_id, **_full_plan_kwargs(steps_in))
+    env = await c.i_will_work_on(
+        agent_id=dev_id, task_id=task_id, **_full_plan_kwargs(steps_in)
+    )
     body = env.as_dict()
     assert body.get("error") != "incomplete_input", body
     # The full rich plan was layered into the panel-shaped dict and persisted,
@@ -188,8 +190,8 @@ async def test_dev_fresh_claim_missing_considerations_and_risks_rejected() -> No
     c = Choreographer(_make_deps(task=_dev_task_svc(task_id)))
 
     env = await c.i_will_work_on(
-        dev_id,
-        task_id,
+        agent_id=dev_id,
+        task_id=task_id,
         plan=_GOOD_PLAN,
         steps=[{"title": "Edit README", "description": _GOOD_STEP_DESC}],
     )
@@ -210,7 +212,9 @@ async def test_dev_reentry_in_progress_short_circuits_before_steps_gate() -> Non
     svc.get.return_value.assigned_to = dev_id
     c = Choreographer(_make_deps(task=svc))
 
-    env = await c.i_will_work_on(dev_id, task_id, plan="resume: keep going")
+    env = await c.i_will_work_on(
+        agent_id=dev_id, task_id=task_id, plan="resume: keep going"
+    )
     body = env.as_dict()
     assert body.get("error") is None, body
     assert body.get("status") == "in_progress", body