test: cover daemon socket path and pid utilities

[ZayanKhan-12]

Why

src/daemon/utils.ts exports the functions that decide where the daemon socket and pid files live and whether a daemon is alive (getRuntimeHome, getSocketPath, getPidFilePath, getDaemonPid, isDaemonRunning), but tests/daemon/utils.test.ts only covered serializeArgs and assertValidSessionId. This adds direct unit coverage for the path-resolution and pid-lifecycle logic (243 added lines, tests only — no src/ changes).

Coverage

• getRuntimeHome: XDG_RUNTIME_DIR respected / unset fallback, invalid session-id rejection
• getSocketPath: unix socket path shape (with/without XDG_RUNTIME_DIR), Windows named-pipe format (platform-gated), invalid session-id rejection
• getPidFilePath: daemon.pid inside the runtime home, invalid session-id rejection
• getDaemonPid: missing file → null, whitespace tolerance, per-session scoping, empty/non-numeric contents → null, leading-integer parsing of malformed contents
• isDaemonRunning: no pid file → false, live process (own pid) → true, dead process (exited child pid) → false

Env vars are saved/restored in hooks; pid files are written under mkdtemp temp dirs, nothing touches real daemon state.

Testing

• node scripts/test.js tests/daemon/utils.test.ts → pass (exit 0)
• npm run test:no-build → full suite pass (exit 0)
• npm run check-format → eslint + prettier clean

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