Add idle-state classifier and Solo-parity timer tools

Classifies every running child as idle/working/thinking/permission/error
using one of three pluggable strategies (output_activity,
osc_title_stability, osc_title_status) plus optional regex promoters
applied to the tail of recent output. State and last-match reason are
exposed via MCP on ProcessInfo and get_process_status. Per-preset
configuration lives on a new preset.IdleDetection block with bundled
defaults for the first-party claude/codex/opencode presets.

OSC title plumbing is exposed as Emulator.Title(), polled from the
session pump after each emulator write so title-change activity feeds
into the classifier without an extra cgo callback.

The MCP timer surface expands to match Solo: timer_set,
timer_fire_when_idle_any/all, timer_cancel, timer_pause, timer_resume,
timer_list. timer_wait is now a thin wrapper that shares the same
manager so it shows up in timer_list while pending. Timer bodies are
delivered to the owner process through the existing
InjectAsOrchestrator path. Top-level (non-agent) callers can attach
timers to a specific process via owner_process_id; omitting it grants
universal cancel/pause/resume/list privileges.

The sidebar gains a state glyph per process row and appends a
nearest-timer indicator when one is pending or paused.

Tests: idle_test.go covers the classify() pure function across the
three strategies and regex promotion; timers_test.go covers the
manager. Harness scenarios cover output_activity, osc_title_stability,
osc_title_status, and regex promotion, plus timer_set delivery,
cancel, pause/resume, idle_any-on-transition, idle_all-pending, and
idle_all-already-satisfied. A new wait_until_mcp harness step type
polls an MCP method until an assertion holds.

internal/app/app.go

@@ -113,6 +113,11 @@ func Run(ctx context.Context, opts Options) error {
 	ctx, cancel := context.WithCancel(ctx)
 	defer cancel()
 
+	// Per-session idle-detection classifier. One goroutine ticks every
+	// 250ms over every live child and updates IdleState. It stops when
+	// ctx is cancelled.
+	go sess.runClassifier(ctx)
+
 	st := &uiState{
 		sess:       sess,
 		presets:    presets,
@@ -120,6 +125,7 @@ func Run(ctx context.Context, opts Options) error {
 		pads:       pads,
 		chromeWake: make(chan struct{}, 1),
 		trust:      trustStore,
+		timers:     host.timers,
 		hostCols:   cols,
 		hostRows:   rows,
 		stdinTTY:   term.IsTerminal(int(os.Stdin.Fd())),
@@ -296,6 +302,7 @@ type uiState struct {
 	launcher *Launcher
 	pads     *scratchpad.Store
 	trust    *trust.Store
+	timers   *timerManager
 
 	outMu sync.Mutex
 
@@ -610,6 +617,14 @@ func (st *uiState) OnChildSpawned(c *Child) {
 	st.drawStatusLine()
 }
 
+// OnChildStateChanged repaints the sidebar whenever a child's
+// idle-state badge flips. Cheap — the badge is the only chrome that
+// reflects state today, and drawSidebar bails when the cached frame
+// hasn't changed.
+func (st *uiState) OnChildStateChanged(string, IdleState) {
+	st.drawSidebar()
+}
+
 // OnChildExited drops focus and shows the empty state if it was the
 // focused child.
 func (st *uiState) OnChildExited(c *Child) {