[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.

docs/rag/workflows/megatask.md

@@ -14,7 +14,7 @@ Hierarchy: Umbrella (Main PM) → Root-subtasks (Main PM) → Cell tasks (cell P
 - The umbrella does **no git**. It is exempt from the branch gate (it reaches `in_progress` with no branch) and you must **not** call `submit_root` on it — it assembles no PR. Each root-subtask opens and is reviewed on its own PR.
 - The umbrella **completes** only when every root-subtask is terminal; then it escalates to the CEO (PR requirement waived).
 - The root-subtasks are sequenced: a wave's tasks dispatch only once the previous wave's tasks reach a terminal state (ordinary dependency-gating). You do not reorder them — the analyzer set the order at create time.
-- On the Board route the root-subtasks are held in `backlog` until the CEO approves the umbrella, then released to `pending`. On the Approve & Start route they start immediately.
+- On the Board route the root-subtasks are held in `backlog` until the CEO approves the umbrella, then released to `pending`. On the Approve & Start route they start immediately. On Board-route activation a `code`-typed root-subtask is **retyped to `planning`** — a Main PM never owns a `code` task (the `main_pm + code` combo is the 2026-06-27 meltdown trigger).
 
 ## For the Main PM