[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/optimal_brain/test_replace_chunks_atomic.py

@@ -1,16 +1,7 @@
-"""F108 — ``VectorStore.replace_chunks`` must be a single atomic transaction.
-
-The replace-on-reingest path used to be ``delete_by_source`` (one pool
-connection) followed by ``add_chunks`` (a *second* pool connection). Two
-concurrent re-indexes of the same source interleaved across those two
-connections and produced duplicate chunk rows; an add failure after a
-successful delete also lost the source's index rows. The fix is a single
-``replace_chunks(source, chunks)`` that deletes + inserts on ONE connection
-inside ONE asyncpg transaction, so the whole replace is atomic.
-
-These tests mock the asyncpg pool/connection to assert the atomicity
-invariant (single acquire, transaction entered, delete + insert on the
-same connection) without standing up a pgvector DB.
+"""``VectorStore.replace_chunks`` is a single atomic transaction: delete +
+insert on ONE connection inside ONE asyncpg transaction, so concurrent
+re-indexes can't interleave and an insert failure can't lose the source's
+rows. These tests mock the asyncpg pool to assert that invariant.
 """
 
 from __future__ import annotations