docs: fix review findings — residual ordinals, hypothetical IPC row, citation-rule amendments

Purge the residual task/phase ordinals review caught ((T2), (queue cut 1)
×3, T6, P-I, 'this cut' ×6 including battery-expansion finds in two
untouched notes and a workflow JSDoc); drop the 'externally logged as
Decision 21' parenthetical and rename the remaining bare decision-21
mentions; mark the gui-layering IPC bridge row as a hypothetical example;
restore the GATE_NOTICE doc-typecheck clause and the py-types 'measured'
provenance; say subprocess-backed in filesystem.md; add the picker note
path. Amend the citations note: merged-PR evidence anchors in Agent Notes
are sanctioned, and the candidate gate patterns gain the four shapes the
sweep missed. All nine touched pairs re-recorded.

packages/hooks/hooks-claude/src/index.ts

@@ -349,7 +349,7 @@ function stopPayload(ctx: Context, agent: Agent): Record<string, unknown> {
  * Build a SubagentStart/SubagentStop payload from the CC base (the child's
  * `session_id`/`cwd` when the child agent is available) plus the subagent-hook
  * fields. `agent_type` is the CC-default {@link SUBAGENT_TYPE}; `stop_hook_active`
- * is present on SubagentStop only (the loop-guard flag, always false this cut).
+ * is present on SubagentStop only (the loop-guard flag, always false).
  */
 function subagentPayload(ctx: Context, event: 'SubagentStart' | 'SubagentStop', info: { id: string }, child: Agent | undefined): Record<string, unknown> {
   return {