fix(rebase): migrate the replayed stack onto current master APIs

The linear replay carried each commit's own lineage, so this checkpoint
restores the master-owned surfaces the conflicted regions clobbered and
migrates branch-owned code to master's post-rebase APIs:

- rebuild subprocess-local spawn.ts on master's tree-exit-observer
  machinery, keeping the branch's win32 childEnv key semantics and the
  Linux zombie-quiescence probe; the zombie test reaps its survivor
  directly since a confirmed-absent verdict is a permanent
  no-more-signals boundary
- migrate pty-local test stubs to the Inbox-model Agent interface,
  Session.create, runnerFailureRules, and the new turn/start payload
- implement the seam's resolveExecutable/spawnTerminal abstracts in the
  new pwsh-local and tool-fs-search test fakes
- restore code-runtime, atomic-write, pwsh-local, and app-boot to
  master's exact content (the net-zero code-runtime churn is pruned
  from this history) and drop rename-detection graft debris
- re-apply the PR's architecture rows and execution-world paragraph,
  re-record bilingual pairings, regenerate catalogs, and reconcile the
  lockfile

.agents/notes/implemented/architecture/2026-07-20-canonical-tool-output-contract.i18n.yaml

@@ -3,4 +3,4 @@
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write .agents/notes/implemented/architecture/2026-07-20-canonical-tool-output-contract.md
 2026-07-20-canonical-tool-output-contract.md: 2429e1c141ad8c8ee932c6d654a6ba74bc4f7618
-2026-07-20-canonical-tool-output-contract.zh.md: fd1e55eab38e5929a2dc104073b49f9de7a493e2
+2026-07-20-canonical-tool-output-contract.zh.md: 26653ea769b8a642b70c4d3dd2f5ab907a70bd85