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

THIRD_PARTY_NOTICES.md

@@ -57,6 +57,8 @@ External packages that a workspace package resolves at runtime. `scripts/install
 | [`clsx`](https://github.com/lukeed/clsx) | MIT |
 | [`commander`](https://github.com/tj/commander.js) | MIT |
 | [`diff`](https://github.com/kpdecker/jsdiff) | BSD-3-Clause |
+| [`dotenv`](https://github.com/motdotla/dotenv) | BSD-2-Clause |
+| [`e2b`](https://github.com/e2b-dev/e2b) | MIT |
 | [`eventsource-parser`](https://github.com/rexxars/eventsource-parser) | MIT |
 | [`handlebars`](https://github.com/handlebars-lang/handlebars.js) | MIT |
 | [`immer`](https://github.com/immerjs/immer) | MIT |