docs(code-runtime): fix remaining dunder/backend wording and document exports in README

- index.ts: RESERVED_ERROR_MEMBERS JSDoc now says `__x__` (non-empty
  middle), matching DUNDER_MEMBER and the derivative docs; and
  PORTABLE_RESERVED_WORDS is described as covering portable *target*
  languages (Python is a later-PR backend, not yet shipped).
- types.ts + type-equiv docs: CodeBindingNamespace.global points to
  RESERVED_BINDING_GLOBALS by name with an `e.g.` sample rather than
  enumerating the set (single home), no longer implying `__debug__` is a
  seeded slot.
- Agent Note: separate `__debug__` (CPython compile-time constant) from
  the seeded bootstrap globals.
- README (en/zh): document the four exported exclusion sets and the
  portable identifier/naming contract — no cross-package link needed.
- Regenerate cordis services catalog for the shifted source line.

packages/code-runtime/code-runtime/README.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write packages/code-runtime/code-runtime/README.md
-README.md: c7a2d519e47d160f5ab123bfc887e7e9f24ec602
-README.zh.md: 22d0b120d7cea50b578a184b3e40d77707ebc489
+README.md: fafaca85ac63e83e16882ef17f9f8995103866fd
+README.zh.md: dc771bc16557d4b68529f2fde29eef1c09f299b5