fix(rebase): migrate the replayed E2B branch onto the rebased parent

The linear replay carried old-lineage content over parent-owned files;
this checkpoint restores them and adapts the branch to the parent's
post-rebase seam:

- restore all pty/lsp/subprocess/code-runtime surfaces to the parent's
  exact content (this branch claims none of them) and drop the net-zero
  code-runtime-e2b/pty-e2b/lsp-e2b residue and its registrations
- widen serializeRemoteEnvironment to the seam's NodeJS.ProcessEnv
  tombstone contract: an explicit undefined removes an ambient entry
- migrate the two E2B fixture Agent stubs to the Inbox-model interface
  and Session.create
- re-apply the branch's gen-doc-graphs roles, THIRD_PARTY_NOTICES e2b
  row, and packages/README group row (trimmed to the doc budget);
  regenerate catalogs and re-record bilingual pairings

packages/pty/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/pty/README.md
-README.md: a6706ed653bc60909a23b3598c41bb10ef499cbe
-README.zh.md: 01fecf8d57d933168e91331c4d3c3e4666c13cdc
+README.md: a4f743056b4a524be9623b0f700f37e0534b463f
+README.zh.md: c84ad3f1b59afcdbbd111f1b82c57c56aa24fdcf