fix(cli): contain app-exit races in watcher setup; sync watch docs

A fast one-shot can request exit through ctx.appExit while the launcher
still awaits its watcher setup; the failure guard now also swallows the
resulting rejections when the tree is no longer live, not only on
signal shutdown. Sync the app-boot README and headless bundle comment
with unconditional patch watching, and bring the two Agent Notes still
asserting the --dev row append and the headlessIo slot current.

packages/bundle/headless/cordis.patch.yml

@@ -9,7 +9,8 @@
     persona: >-
       You are a coding agent powered by the {{model}} model. Your working directory is {{cwd}}.
 
-# One-shot runs never watch or reload their composition.
+# The shared module-reload HMR row stays off; the launcher's watch-only
+# fallback still keeps the user patch layers live until the run exits.
 - id: hmr
   disabled: true