fix(docs): address Codex review round 2 — repoint every remaining moved-policy citation

The definitive sweep (audit every AGENTS.md mention in packages/, docs/,
examples/, scripts/) found thirteen more citations of relocated policy
and two citations of rules that never existed as quoted:

- with-key policy comments (web deepseek/perplexity e2e headers) ->
  docs/testing.md; real-impl-over-mock comments (acp harness, load,
  stream-update specs) -> docs/testing.md; defensive-pattern quotes
  (acp index.ts x3, stream-update) -> docs/defensive-patterns.md.
- md-tier repoints: real-api-e2e RFC, tool-schema-catalog RFC,
  postmortem 0001 guardrail row, adding-a-package cookbook,
  drop-bash-output-spill-files RFC, acp-subagent-backend RFC phrasing.
- Two false attributions dropped in favor of self-contained reasoning:
  tool-todo's 'don't validate scenarios that can't happen' and the
  bash-stdin-env RFC's 'Don't add features beyond what the task
  requires' (neither rule ever existed under those names).
- Citations of the two 'not golden truth' doctrines stay: those bullets
  survive verbatim in the root conventions.

Note: packages/support/ui-stdio readline TTY spec flakes under full
coverage on a heavily loaded box (passes standalone and passed the
same tree's coverage run minutes earlier); untouched by this stack.

docs/postmortem/0001-acp-default-export-drops-inject.md

@@ -101,7 +101,7 @@ Both bugs share one root process gap: **no test exercised the plugin through its
 - **`AgentLoop.resume` reads `this.ctx.get('sessionPersistence')`** (`packages/core/agent-loop/src/index.ts`) — the Bug #2 fix, with a comment explaining the shadow-walk trap.
 - **No-key `session/new` e2e over real stdio** (`examples/acp-agent/tests/acp.e2e.ts`): boots the example as a subprocess through the real Loader and asserts `session/new` resolves. This fails loudly on Bug #1 with no API key. Verified it fails when `export default apply` is restored.
 - **`TSX_TSCONFIG_PATH` in the e2e spawn**: the subprocess runs from a temp cwd, where tsx cannot find the repo-root tsconfig `paths` map by searching upward — so dsh-* imports silently fell back to built `lib/`. Pointing tsx at the repo tsconfig makes resolution cwd-independent and ensures the test runs *source*, not a possibly-stale build.
-- **AGENTS.md defensive pattern**: "Line coverage is not behavior coverage; test the REAL entry path, not a synthetic stand-in" — codifies the lesson for every future plugin.
+- **[docs/testing.md](../testing.md) rule**: "test the real entry path", line coverage is not behavior coverage — codifies the lesson for every future plugin.
 
 ## Lessons