feat: add OpenCode V2 plugin support (dual V1/V2 entry)

[vheins]

Summary

Adds OpenCode V2 support to opencode-smart-voice-notify while keeping full V1 backward compatibility.

OpenCode v2.0.x loads plugins through the new @opencode/plugin API and requires the module's default export to be an object with id plus setup (or effect). The current 1.4.0 default export is a V1 async function, so V2 fails to load the plugin with:

PluginModule.LoadError: Plugin must export a default definition with an id and an effect or setup function.
(cause: SchemaError(Expected object at ["default"]))

This PR makes the plugin load and work on both V1 (1.18.29+) and V2 (2.0.x).

What changed

• Dual entry point (src/index.ts): default export is now { id, setup, server } — V2 reads id/setup, V1 reads server. The original V1 implementation is preserved verbatim as a named export in src/plugin.ts.
• V2 adapter (src/v2.ts):
  • Builds a V1-compatible $ shell runner on top of node:child_process (V2 has no shell runner) with .quiet()/.nothrow()/.timeout().
  • Provides a client shim (session.get → ctx.session.get; toast is a no-op since V2 exposes no plugin toast API).
  • Translates V2 events ({ type, data }) into the V1 { type, properties } shape so the battle-tested notification engine is reused unchanged.
  • Subscribes via ctx.event.subscribe() and disposes cleanly.
• Event mapping for V2, including the important one: V2 defines session.idle in its schema but never emits it — the real completion signal is session.execution.succeeded. Mapping:
  • session.execution.succeeded → session.idle (agent finished)
  • session.execution.failed → session.error
  • permission.asked → permission.v2.asked
  • form.created / form.replied / form.cancelled → question.v2.asked / question.v2.replied / question.v2.rejected
  • session.inbox.enqueued (user item) → message.updated (user-activity signal)
• Cross-instance correctness: V2 loads the plugin once per location but every instance shares one process-wide event stream. Two guards prevent duplicate/echoed audio:
  • Process-wide event-id de-duplication.
  • Location filtering, with a session→location registry so location-less events (e.g. session.execution.succeeded) are routed to the correct instance.
• Install/packaging fixes for V2 git installs:
  • Root server.js re-export bridge + ./server export (V2 resolves an absolute plugin directory via its server entrypoint).
  • Rename build/build:types scripts → compile/compile:types so pacote's git-dependency preparation no longer triggers a failing npm install --force (the prepare-triggering build script was the cause).
  • Move msedge-tts to optionalDependencies (its preinstall: only-allow pnpm breaks npm-based git installs; it is only used as a lazy fallback for the edge engine).
  • dist/ stays git-ignored and is produced by the existing compile script as before.
• Tests: new tests/unit/v2-adapter.test.ts covering entry shape, all event translations, the shell shim, the client shim, setup() wiring, de-duplication, and session→location routing. Existing tests updated to import the V1 function as a named export.

Compatibility

• V1: unchanged behavior via the server field.
• V2: full support. One caveat — V2 exposes no plugin-facing toast API, so the in-terminal toast is a no-op on V2; desktop notifications, sound, TTS, webhooks, and AI messages all work.

Testing

• bun run typecheck — clean
• bun run compile — clean
• bun test — 765 pass / 17 skip / 1 fail. The single failure is pre-existing and unrelated (tests/unit/vscode-focus.test.ts → spyOn(target, prop) does not support accessor properties yet); it fails identically on the unmodified baseline.

Verified end-to-end on OpenCode v2.0.18: the plugin loads, completion notifications fire once (no echo), and permission/question/error paths work.