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/architecture/preconditions-and-rejections.md

@@ -90,7 +90,7 @@ def _check_intent_preconditions(
     spec_intent: IntentSpec, task: Any, ctx: Context
 ) -> Decision | None:
     """Verb-level extra_preconditions gate.
-    
+
     If the first failing precondition has rejection_kind='not_authorized',
     return Decision.reject(kind='not_authorized').
     All other failures return Decision.tracing_gap.
@@ -102,12 +102,11 @@ def _check_intent_preconditions(
     ]
     if not missing:
         return None
-    
+
     first_missing = next(
-        p for p in spec_intent.extra_preconditions 
-        if p.missing_token == missing[0]
+        p for p in spec_intent.extra_preconditions if p.missing_token == missing[0]
     )
-    
+
     # Check the rejection_kind of the first failing precondition
     if first_missing.rejection_kind == "not_authorized":
         return Decision.reject(
@@ -115,12 +114,9 @@ def _check_intent_preconditions(
             message=first_missing.remediate,
             remediate=first_missing.remediate,
         )
-    
+
     # Default: tracing_gap with missing tokens
-    return Decision.tracing_gap(
-        missing=missing, 
-        remediate=first_missing.remediate
-    )
+    return Decision.tracing_gap(missing=missing, remediate=first_missing.remediate)
 ```
 
 The key insight: **Only the first failing precondition's `rejection_kind` is checked.** This ensures ownership gates are checked early (they usually are in the preconditions list) so unowned tasks fail fast with `not_authorized` instead of collecting other tracing gaps.