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.

.agents/notes/implemented/architecture/2026-07-31-code-runtime-portable-identifier-seam.md

@@ -15,7 +15,7 @@ A second backend written against a different language (CPython, arriving in a la
 The seam package (`@deepseek-ai/dsh-code-runtime`) exports the portable-identifier exclusion contract as four named constants, and every backend imports them rather than re-declaring:
 
 - `PORTABLE_RESERVED_WORDS` — the union of ECMAScript and Python reserved words. A namespace global or error-class name matching any is refused on all backends, so `lambda` is refused even though it is a legal JS parameter name. Adding a language widens this union, which is a deliberate breaking review of existing binding names.
-- `RESERVED_BINDING_GLOBALS` — globals some backend owns in the program's namespace: `console` (the worker's log capture) and `__dsh_main__`/`__builtins__`/`__name__`/`__debug__` (the Python bootstrap's wrapper and seeded module globals). Refused everywhere so a namespace list cannot pick a name that works on one backend and collides on another.
+- `RESERVED_BINDING_GLOBALS` — globals some backend owns in the program's namespace: `console` (the worker's log capture), `__dsh_main__`/`__builtins__`/`__name__` (the Python bootstrap's wrapper and seeded module globals), and `__debug__` (not a seeded slot but a CPython compile-time constant that rejects assignment, so an injected global under that name is unreachable — the same portability split by a different mechanism). Refused everywhere so a namespace list cannot pick a name that works on one backend and collides on another.
 - `RESERVED_ERROR_MEMBERS` — error-member names every backend refuses: the JS `Error` slots (`name`, `message`, `stack`) and Python's exception-protocol members (`args`, `with_traceback`, `add_note`).
 - `DUNDER_MEMBER` — the dunder-form regex (`__x__`, non-empty middle), refused as an error member wholesale because several are constrained CPython descriptors whose exact set is an interpreter-version detail.