Adapter: tell the factory when a thread's run changes status #7

Outcome

The factory hears about a session finishing within seconds instead of waiting for its next pass.

Acceptance criteria

• apps/server/src/factory/t3/events.ts provides a Stream of thread ids built on EventSinkV2.stream. It emits a thread's id each time that thread's latest run changes status.
• The stream starts at the live position when the server starts and replays no history.
• A contract test with the test provider launches a thread and sees its id on the stream within 10 s of the run completing.

Depends on

• Adapter: find a project, launch a thread and read its status in-process #5

Notes

Reference

• softfac, the Rust factory this ports, pinned at rawphp/softfac@bf273a1. Read it from a separate clone: git clone --filter=blob:none https://github.com/rawphp/softfac /tmp/softfac-ref && git -C /tmp/softfac-ref checkout bf273a1d93651992b4fc95b4dd6c111f8f3322cf. Its docs/lifecycle.md, docs/reference/ledger.md and docs/issues.md describe the behaviour; its tests pin it.
• Design: factory/docs/design.md in this repo.
• Upstream's AGENTS.md applies. Run only the tests and typechecks for the paths you touch (vp test run <path>, vp run --filter t3 typecheck), never the repo-wide checks.
• Edit no upstream file that is not listed in factory/SEAMS. A new seam needs a line in factory/SEAMS and a reason in the PR body.
• Port behaviour, not code: port the named test cases first (TypeScript, vitest / @effect/vitest), then make them pass. Exact comment and ledger wording is ported as is.