refactor: eliminate Instance.state() — convert 16 modules

[e6qu]

Summary

• Convert all 16 Instance.state() modules to module-level Map<directory, state> with registerDisposer() for lifecycle cleanup
• Delete State module (src/project/state.ts) and remove state() method from Instance
• Delete Scheduler module (src/scheduler/index.ts) — replaced by inline setInterval in bootstrap
• Register 4 new Effect services in instances.ts: EnvService, BusService, SessionStatusService, InstructionService
• 11 modules use registerDisposer directly (Config, TuiConfig, Plugin, ToolRegistry, Provider, Agent, Command, Prompt, PTY, LSP, MCP) — can't be in instances.ts due to circular import constraints

Modules converted (by stage)

Stage	Modules
1 — Trivial	Env, SessionStatus, Instruction
2 — Bus + Scheduler	Bus (converted), Scheduler (deleted)
3 — Config	Config, TuiConfig
4 — Plugin + Registry	Plugin, ToolRegistry
5 — Provider + Agent	Provider, Agent
6 — Command + Prompt	Command, Prompt
7 — Lifecycle	PTY, LSP, MCP
8 — Cleanup	Remove Instance.state(), delete State module

Test plan

• bun typecheck — 0 errors across all 13 packages
• bun test — 1423 tests pass, 0 failures
• grep -rn 'Instance\.state(' packages/opencode/src/ — 0 results
• Dispose logic preserved for lifecycle services (PTY kills processes, LSP shuts down clients, MCP kills descendants)