feat(bus): migrate Bus to Effect service with PubSub

[kitlangton]

Summary

Migrate the Bus service to Effect with PubSub internals, and make a deliberate semantic change: publish is now fire-and-forget — it no longer blocks on subscriber callbacks completing.

Bus Effect Service

• Add Bus.Service as a ServiceMap.Service backed by Effect PubSub
• publish(def, props) → Effect<void> — pushes to per-type + wildcard PubSubs and emits to GlobalBus
• subscribe(def) → Stream<Payload<D>> — returns a typed stream via Stream.fromPubSub
• subscribeAll() → Stream<Payload> — returns a wildcard stream
• Legacy adapters wrap the Effect service: publish via runPromiseInstance, subscribe/subscribeAll via runCallbackInstance (returns interruptor as unsubscribe)
• Add runCallbackInstance helper to effect/runtime for long-lived stream subscriptions

Type tightening

• GlobalBus payload: any → { type: string; properties: Record<string, unknown> }
• BusEvent.define: constrain Properties to ZodObject instead of ZodType, so TS knows event properties are always a record
• Refactor watcher test to use Bus.subscribe instead of raw GlobalBus listener

Behavioral changes

Publish is fire-and-forget. The old Bus awaited Promise.all of subscriber callbacks before returning. With PubSub, publish enqueues messages and returns immediately. This is intentional — a pub/sub system that blocks on all subscribers is a hidden control-flow dependency, not a bus. One slow listener shouldn't turn the bus into a synchronous pipeline.

We audited every await Bus.publish(...) + subscriber pair in the codebase. The only case where the old blocking behavior was load-bearing was formatting: the write/edit/apply_patch tools published File.Event.Edited, and the formatter subscribed with an async callback that spawned an external process. The old bus happened to await the formatter finishing before the tool continued to stamp FileTime and run LSP diagnostics.

Fix: make formatting explicit. Rather than relying on the bus to implicitly sequence formatting, we now call Format.run(filepath) directly in the write tools, right after Filesystem.write() and before FileTime.read() / LSP diagnostics. This is clearer, more predictable, and means the File.Event.Edited event now reflects the final (post-format) file state. The Bus subscription in the Format layer is removed entirely — File.Event.Edited now has zero local subscribers (it still goes to GlobalBus/SSE for UI consumers).

All other subscriber pairs are either informational (VCS branch detection, share sync, plugin hooks) or have zero subscribers. None depend on publish blocking.

Cleanup

• Remove unused Bus.once (zero callers in codebase)
• Remove Instance.state-based subscription management (replaced by PubSub)
• InstanceDisposed is already emitted to GlobalBus by instance.ts — the Bus no longer duplicates this

Test plan

• Comprehensive bus test suite (15 tests): publish/subscribe, multiple subscribers, unsubscribe, subscribeAll, GlobalBus forwarding, instance isolation, disposal, async subscribers
• Format tests pass (4 tests)
• All existing tests pass (1229 pass, 2 flaky SQLite I/O failures unrelated to changes)
• Typecheck passes across all packages

[kitlangton]

Upstream Effect PRs

This migration uncovered three issues in effect-smol that affect LayerMap-based service lifecycle management:

1. RcMap.invalidate bails on refCount > 0 — fix(RcMap): invalidate should close scope regardless of refCount Effect-TS/effect-smol#1799
2. PubSub.shutdown doesn't interrupt suspended subscribers — Fix PubSub shutdown to interrupt suspended subscribers Effect-TS/effect-smol#1800
3. PubSub.publish returns false on shutdown instead of interrupting — PubSub.publish returns false on shutdown instead of interrupting Effect-TS/effect-smol#1802
4. Stream.fromPubSub doesn't propagate interrupts on PubSub shutdown — Stream.fromPubSub propagates interrupts on PubSub shutdown Effect-TS/effect-smol#1804

Once these land, the GlobalBus bridge in subscribeAll can be removed — PubSub shutdown will naturally end streams and fire ensuring callbacks.