Refactor daemon entrypoint back to thin-router responsibilities

[thymikee]

Problem

src/daemon.ts is currently ~593 LOC and exceeds the intended thin-router boundary documented in AGENTS. The file handles broad orchestration concerns beyond minimal routing.

Goal

Restore src/daemon.ts to thin-router responsibilities by extracting orchestration helpers into dedicated modules.

Proposed split

• src/daemon/server-lifecycle.ts
  • startup/shutdown + state/lock coordination helpers
• src/daemon/request-router.ts
  • request dispatch orchestration across handlers
• src/daemon/transport.ts
  • transport-specific helper logic (if not already encapsulated)
• Keep src/daemon.ts as minimal entrypoint + wiring.

Acceptance criteria

• No behavior change in daemon startup, routing, or shutdown semantics.
• Handler ownership boundaries remain intact (session/interaction/snapshot/find/record-trace).
• New modules target <=300 LOC where practical.
• src/daemon.ts is substantially reduced and easier to audit.

Validation

• pnpm typecheck
• pnpm test:unit
• pnpm test:smoke