fix(subagent): carry routing provenance end to end and validate it structurally

- the Agent tool forwards routing and the current revision on
  subagent.spawned, so the web roster shows provenance for normal launches
- the web projector keeps the spawned provenance when task.started omits it
  instead of overwriting it with undefined
- REST and event routing mappers reject values outside the contract instead
  of casting them through
- the persisted provenance event and replayable key use a structural Zod
  schema instead of z.custom without a predicate
- spawn tests assert the handoff the service owns; the vacuous resume
  assertion is removed

Author: elkaix

apps/pythinker-code/dist-web/.web-bundle-manifest.json

@@ -1,4 +1,4 @@
 {
-  "sourceHash": "835f2c31f60a0ca2bb84b73a82efcd0cdaa62f220810afc1b99ad80846868f51",
+  "sourceHash": "4dfb056fc19c689c0659001027d42871db38c11b771601d71926aec9db1b6ab2",
   "sourceFileCount": 405
 }