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/workflows/kb-search.md

@@ -25,9 +25,9 @@ It searches ALL knowledge sources and supports follow-up questions.
 ```python
 roboco_kb_search(
     query="rate limiting redis implementation",
-    top_k=5,                      # Results to return
-    project="roboco-api",         # Optional project filter
-    index_types=["code", "docs"]  # Filter by type
+    top_k=5,  # Results to return
+    project="roboco-api",  # Optional project filter
+    index_types=["code", "docs"],  # Filter by type
 )
 ```
 
@@ -36,10 +36,7 @@ Returns similar content - not just keyword matches.
 ## RAG Query (AI Answer)
 
 ```python
-roboco_rag_query(
-    query="How does authentication work in this codebase?",
-    top_k=5
-)
+roboco_rag_query(query="How does authentication work in this codebase?", top_k=5)
 ```
 
 Returns AI-synthesized answer with citations.
@@ -54,14 +51,12 @@ Good for:
 ```python
 # First question
 response = roboco_ask_mentor(
-    question="How do I handle authentication?",
-    domain="coding"
+    question="How do I handle authentication?", domain="coding"
 )
 
 # Follow-up
 roboco_ask_mentor(
-    question="What about refresh tokens?",
-    conversation_id=response["conversation_id"]
+    question="What about refresh tokens?", conversation_id=response["conversation_id"]
 )
 ```