Dual-protocol client: OpenCode V1 and V2 wire APIs

[jensenojs]

Summary

Reworks the client to speak both OpenCode wire protocols (V1 1.18.x and V2 2.0.x) through a single connection/observation architecture.

What changed

• New protocols/{v1,v2} modules own native endpoints and event interpretation per protocol; ui/ consumes one read-only per-session Observation instead of reducing protocol events.
• Connection selection: authenticated health probe picks the protocol once per connection; reconnect on identity change, no per-request branching.
• V2 uses the native shared service via CLI discovery (service status / get password); V1 keeps local spawn, explicit URLs, and port coordination.
• Removed api_client, event_manager, session, renderer/events, event_scope, session_scope.
• Topbar cost/context stats now derive from observation usage (V2 session.usage.updated / snapshot first, latest entry fallback for V1).
• run_tests.sh now names the spec file when a test file dies at load time (e.g. requiring a removed module), instead of a bare non-zero exit.

Contract

The published OpenAPI spec and the running 2.0.x server disagree at several endpoints (/api/project/current, rename via POST, prompt command field, fork body shape). This implementation follows the running server; fixtures under tests/data/v2/ are live captures from a real 2.0.1 server. Known future break: upstream dev renames permission.asked / form.* events.

Details in docs/drafts/v2-migration-draft.md (temporary draft intended to be folded into docs later).

Testing

• ./run_tests.sh green (minimal, unit, replay).
• Per-protocol contract suites: protocol_{v1,v2}_{operations,observation}*_spec.lua.
• Live dual-client check done against a real 2.0.3 shared service (native discovery, auth, event stream, prompt admission, both TUI↔nvim visibility).