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_choreographer_claim_guards.py

@@ -131,7 +131,9 @@ async def test_i_will_work_on_blocks_when_agent_has_in_progress_task() -> None:
     deps = _make_deps(task=task_svc)
     c = Choreographer(deps)
 
-    env = await c.i_will_work_on(agent_id, target_id, plan="x", steps=_STEPS)
+    env = await c.i_will_work_on(
+        agent_id=agent_id, task_id=target_id, plan="x", steps=_STEPS
+    )
     body = env.as_dict()
     assert body["error"] == "invalid_state"
     assert str(other_id) in body["message"] or str(other_id) in body["remediate"]
@@ -165,7 +167,7 @@ async def test_i_will_work_on_resumption_does_not_self_block() -> None:
     deps = _make_deps(task=task_svc)
     c = Choreographer(deps)
 
-    env = await c.i_will_work_on(agent_id, task_id, steps=_STEPS)
+    env = await c.i_will_work_on(agent_id=agent_id, task_id=task_id, steps=_STEPS)
     assert env.error is None
     task_svc.start.assert_awaited_once_with(task_id, agent_id)
 
@@ -195,7 +197,9 @@ async def test_i_will_work_on_blocks_when_agent_has_paused_task() -> None:
     deps = _make_deps(task=task_svc)
     c = Choreographer(deps)
 
-    env = await c.i_will_work_on(agent_id, target_id, plan="x", steps=_STEPS)
+    env = await c.i_will_work_on(
+        agent_id=agent_id, task_id=target_id, plan="x", steps=_STEPS
+    )
     body = env.as_dict()
     assert body["error"] == "invalid_state"
     assert str(paused_id) in body["remediate"]
@@ -226,7 +230,9 @@ async def test_cell_pm_cannot_claim_code_task_via_i_will_work_on() -> None:
     deps = _make_deps(task=task_svc)
     c = Choreographer(deps)
 
-    env = await c.i_will_work_on(pm_id, task_id, plan="x", steps=_STEPS)
+    env = await c.i_will_work_on(
+        agent_id=pm_id, task_id=task_id, plan="x", steps=_STEPS
+    )
     body = env.as_dict()
     assert body["error"] == "not_authorized"
     # Spec produces "role 'cell_pm' may not call 'i_will_work_on'".
@@ -253,7 +259,9 @@ async def test_main_pm_cannot_claim_code_task_via_i_will_work_on() -> None:
     deps = _make_deps(task=task_svc)
     c = Choreographer(deps)
 
-    env = await c.i_will_work_on(pm_id, task_id, plan="x", steps=_STEPS)
+    env = await c.i_will_work_on(
+        agent_id=pm_id, task_id=task_id, plan="x", steps=_STEPS
+    )
     body = env.as_dict()
     assert body["error"] == "not_authorized"
 
@@ -403,7 +411,7 @@ async def test_developer_cannot_claim_qa_status_task() -> None:
     deps = _make_deps(task=task_svc)
     c = Choreographer(deps)
 
-    env = await c.i_will_work_on(dev_id, task_id, steps=_STEPS)
+    env = await c.i_will_work_on(agent_id=dev_id, task_id=task_id, steps=_STEPS)
     body = env.as_dict()
     assert body["error"] == "not_authorized"
     assert "developer" in body["message"]
@@ -494,7 +502,9 @@ async def test_non_developer_role_cannot_claim_via_i_will_work_on() -> None:
     deps = _make_deps(task=task_svc)
     c = Choreographer(deps)
 
-    env = await c.i_will_work_on(doc_id, task_id, plan="x", steps=_STEPS)
+    env = await c.i_will_work_on(
+        agent_id=doc_id, task_id=task_id, plan="x", steps=_STEPS
+    )
     body = env.as_dict()
     # Role-typed claim refuses with not_authorized
     assert body["error"] == "not_authorized"