0.4.0: close the gaps between definition and the legacy authoring surface

[bweis]

What

0.4.0 makes the definition + bundle + activities + client/engine-client + testing surface complete enough that an application never imports the legacy modules, then deprecates those modules for deletion in 0.5.0.

Every gap here is something the Springbird monorepo still had to reach into engine-sandbox, typed-activity, versioning, or mailbox for:

1. Timers on the seam — sleep, sleepUntil from definition (shared timestamp rule sleepUntilTarget). In memory they follow Effect's Clock, so TestClock.adjust drives them and the grace-period race (mailbox take vs timer) is pinned in both orders on both engines.
2. continueAsNew on the seam — in memory it interrupts the fiber and records the continuation (world.continuedAsNewOf(W)), payload round-tripped through the workflow schema.
3. Child workflows on the seam — executeChild(Child, payload, { discard? }); Temporal dispatches into upstream execute (identical commands). makeTestWorkflowOps({ workflows: [handleWorkflow(Child, handler)] }) runs children in-process, forks discarded ones, attaches on a taken id.
4. Type helpers — PayloadOf/SuccessOf/ErrorOf/AnyTypedActivity/… on definition; codecsFor/ACTIVITY_EXIT_TYPE on wire.
5. Client-side driving — every engine-client / WorkflowClient op accepts the declaration directly (or its primitive); new completeDeferred. Fake client: offer/offersTo; harness client: offer/request/stateOf/resolve.
6. versioned(site, { v1, v2 }) — run-table form of version; the main-fiber lint rule recognises it.
7. UpdateRequest — one parameter order (definition's <P, S, E>); the engine-sandbox alias is deprecated.
8. bundle module — workflowBundle's home, "the one file the worker points at"; the rest of engine-sandbox is documented engine-level or deprecated.
9. effect pin → 4.0.0-rc.112.

Deprecations carry @deprecated + replacement; the new prefer-definition lint rule (error in recommended) reports every deprecated import with its replacement. CHANGELOG.md has the 0.5.0 deletion checklist under "Unreleased / planned".

Wire safety

A real defOrder history recorded with the 0.3.0 bundle before any code changed lives in fixtures/histories/; replay-compat.test.ts replays it through this bundle. OrderFlow's handler is byte-for-byte unchanged; the 0.4.0 fixtures sit beside it.

Validation

• typecheck, oxlint, build, docs build (dead links): clean
• full suite: 25 files / 72 tests green, unloaded run (one load-induced batch timeout while two example servers ran concurrently; passes alone and on rerun)
• both examples typecheck and run end to end on the new surface
• consumer checks over examples/: no engine-sandbox import besides workflowBundle, no typed-activity/versioning/mailbox; oxlint with recommended exits 0 there and fails on the deprecated fixtures