[sweep] strip Fxxx audit-ID tokens + trim bloated comments/docstrings + add behavior-change docs

Post-audit sweep over the 135 audit-fix commits since 19a474d3:

1. Stripped every # Fxxx: audit-ID token from comments AND every Fxxx token
   from docstring openings across 211 blocks / ~626 lines. The CEO flagged
   these twice: audit-issue IDs in code confuse future devs/agents. The
   descriptive text is preserved; only the Fxxx token is removed (and bloated
   narrative blocks trimmed to 1-3 lines keeping the one non-obvious invariant).
2. Trimmed bloated comments/docstrings to the concise standard (1-3 lines).
3. Added missing behavior-change docs for the audit-fix batch: prompts/roles
   (documenter, pr_reviewer, qa), user-facing docs (api auth, websockets,
   agent-gateway, megatask, merge-model, task-lifecycle, grok, resilience,
   conventions, panel, security, troubleshooting), and the RAG corpus (cell-pm,
   main-pm, pr-reviewer, qa roles; conventions; messaging-tools; escalation;
   megatask; task-claiming workflows).

Comment/docstring/prose ONLY — zero code-line edits (verified: the diff
contains no def/class/return/if/for/await/assignment/call lines). Gates green:
ruff format + ruff check clean, mypy clean on roboco/. The only pytest failures
are the pre-existing sync_branch tracing-decision gap (B1, 250be5c2) — not
sweep-caused and tracked separately.

tests/unit/services/test_messaging_session_race.py

@@ -1,18 +1,8 @@
-"""F056: ``create_session`` (and its delegate ``get_or_create_active_session``,
-plus the L1868 channel-post adapter that routes through it) must not orphan an
-ACTIVE session under concurrent posts.
+"""``create_session`` must not orphan an ACTIVE session under concurrent posts.
 
-``create_session`` does a plain check-then-create: read ``group.active_session_id``,
-reuse if ACTIVE, else INSERT a new ACTIVE session and point the group at it.
-Two concurrent posts can both miss the active session, both INSERT, and the
-second ``flush`` overwrites ``group.active_session_id`` — the first session
-stays ACTIVE but unreferenced (orphaned) forever. There is no DB uniqueness on
-``(group_id, status='active')`` (tables.py:1121-1125 only carries indexes), so
-nothing stops the double-insert.
-
-The fix: lock the group row (``SELECT ... FOR UPDATE``) and re-read
-``active_session_id`` under the lock before deciding to create, so concurrent
-callers serialize per group and the loser reuses the winner's session.
+Lock the group row (``SELECT ... FOR UPDATE``) and re-read
+``active_session_id`` under the lock before creating, so concurrent callers
+serialize per group and the loser reuses the winner's session.
 """
 
 from __future__ import annotations