Generate Python payload types from a schema derived from shared

[vishnuv688]

Closes #299

The Python adapter hand-mirrored shared's payload types in types.py, and nothing checked the mirror: no mypy runs over the package, so the TypedDicts documented the contract without enforcing it. They had already drifted.

What changes

• Schema from shared's own types. packages/shared/scripts/wire-schema.ts reads WsPayloadFor and a new TraceExportPayloadFor with the TypeScript compiler and writes one JSON Schema per wire scope to packages/shared/wire-schema.json. Scope names and payloads come from shared's existing maps, not a hand list. On the wire a Date is its ISO string and an Error its SerializedError, and the schema says so. packages/shared/tests/wire-schema.test.ts fails when the committed copy is stale, so the Node CI job guards it.
• Generated Python types. gen_contract.py renders the schema into _wire_types.py (36 TypedDicts; required and optional keys split across a base class because typing.Required needs 3.11). types.py re-exports them in place of 151 hand-written lines. The existing drift step diffs the new file too.
• Every sent frame is validated. The eight per-file fake transports in the Python tests become one RecordingTransport that checks each frame against the schema before recording it. Any test that sends anything now fails on an undeclared field, a missing required one, or a null where shared expects the key to be absent.
• TraceLog.suites is tightened from Record<string, unknown>[] to Record<string, SuiteStats>[], which is what every adapter sends, so suite frames are covered too.

Drift the check found, fixed here

Field	Was	Now
callSource (commands, tests)	null when unknown	omitted
metadata.url	null when unknown	omitted
in-flight request status, endTime	null	omitted
unfinished suite state	null	omitted
native session viewport	{width, height}	adds offsetLeft: 0, offsetTop: 0, scale: 1, as core's fromWindow sends

Every reader of those fields in the app, backend and trace uses ?., ??, truthiness or a typeof check, so absent reads the same as null did. ElementScripts is renamed to shared's ElementScriptsResponse; the change fragment is minor for that reason.

Verification

• pnpm test (2506 tests), pnpm lint, pnpm typecheck, pnpm build: green.
• Python unit tests under unittest (707), as CI runs them: green.
• Regenerating both files produces no diff.

Not verified against a live browser: the change is to payload shapes, and each reader of the changed fields was checked in code instead.

[greptile-apps]

Confidence Score: 5/5

[High risk] Regenerates Python payload types from a shared schema.

The PR appears safe to merge; the previous finding is fixed and no new blocking issue was found.

What we checked:

• Bad frames cannot hide: send_json saves violations instead of raising them. The owning test checks them during cleanup, outside the sender's catch block.

Summary

This PR generates Python payload types from shared's TypeScript types and checks test frames against the generated schema.

• Adds schema generation and checks for stale generated files.
• Replaces handwritten Python payload types and fixes fields that had drifted.
• Fixes the previous review finding by checking saved frame violations during test cleanup.
• No new actionable issues were found in the changes since the previous review.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  A["Shared TypeScript payload types"] --> B["wire-schema.ts"]
  B --> C["wire-schema.json"]
  C --> D["gen_contract.py"]
  D --> E["_wire_types.py"]
  E --> F["types.py"]
  C --> G["RecordingTransport checks test frames"]
  G --> H["Saved violations fail test cleanup"]

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_{Reviews (2) · Last reviewed commit: "test(selenium-devtools-py): fail a bad f..." · Reviewed by Greptile}