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/api/test_deps.py

@@ -113,7 +113,9 @@ def test_get_orchestrator_raises_503_when_unset() -> None:
 @pytest.mark.asyncio
 async def test_get_current_agent_id_raises_when_header_missing() -> None:
     with pytest.raises(HTTPException) as exc:
-        await get_current_agent_id(MagicMock(), MagicMock(), x_agent_id=None)
+        await get_current_agent_id(
+            db=MagicMock(), response=MagicMock(), x_agent_id=None
+        )
     assert exc.value.status_code == _HTTP_401
 
 
@@ -125,7 +127,7 @@ async def test_get_current_agent_id_returns_uuid() -> None:
         new=AsyncMock(return_value=expected),
     ):
         out = await get_current_agent_id(
-            MagicMock(), MagicMock(), x_agent_id="be-dev-1"
+            db=MagicMock(), response=MagicMock(), x_agent_id="be-dev-1"
         )
     assert out == expected
 
@@ -133,13 +135,17 @@ async def test_get_current_agent_id_returns_uuid() -> None:
 @pytest.mark.asyncio
 async def test_get_current_agent_slug_raises_when_header_missing() -> None:
     with pytest.raises(HTTPException) as exc:
-        await get_current_agent_slug(MagicMock(), MagicMock(), x_agent_id=None)
+        await get_current_agent_slug(
+            db=MagicMock(), response=MagicMock(), x_agent_id=None
+        )
     assert exc.value.status_code == _HTTP_401
 
 
 @pytest.mark.asyncio
 async def test_get_current_agent_slug_returns_header() -> None:
-    out = await get_current_agent_slug(MagicMock(), MagicMock(), x_agent_id="be-dev-1")
+    out = await get_current_agent_slug(
+        db=MagicMock(), response=MagicMock(), x_agent_id="be-dev-1"
+    )
     assert out == "be-dev-1"
 
 
@@ -494,8 +500,8 @@ def test_coerce_agent_team_empty_returns_none() -> None:
 async def test_get_agent_context_missing_id_raises() -> None:
     with pytest.raises(HTTPException) as exc:
         await get_agent_context(
-            MagicMock(),
-            MagicMock(),
+            db=MagicMock(),
+            response=MagicMock(),
             x_agent_id=None,
             x_agent_role="developer",
         )
@@ -506,8 +512,8 @@ async def test_get_agent_context_missing_id_raises() -> None:
 async def test_get_agent_context_missing_role_raises() -> None:
     with pytest.raises(HTTPException) as exc:
         await get_agent_context(
-            MagicMock(),
-            MagicMock(),
+            db=MagicMock(),
+            response=MagicMock(),
             x_agent_id="be-dev-1",
             x_agent_role=None,
         )
@@ -523,8 +529,8 @@ async def test_get_agent_context_happy_path(monkeypatch: pytest.MonkeyPatch) ->
         new=AsyncMock(return_value=(aid, "be-dev-1")),
     ):
         ctx = await get_agent_context(
-            MagicMock(),
-            MagicMock(),
+            db=MagicMock(),
+            response=MagicMock(),
             x_agent_id="be-dev-1",
             x_agent_role="developer",
             x_agent_team="backend",