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/session.go

@@ -70,6 +70,10 @@ type ChildEventListener interface {
 	// Only the focused-child chunk should reach the screen — the TUI
 	// filters by id.
 	OnPTYOut(childID string, chunk []byte)
+	// OnChildStateChanged fires when the idle-detection classifier
+	// updates a child's IdleState. Listeners use this to repaint the
+	// sidebar badge and to evaluate idle-aware timers.
+	OnChildStateChanged(childID string, state IdleState)
 }
 
 func NewSession(projectDir, projectKey string) *Session {
@@ -140,6 +144,12 @@ func (s *Session) emitPTYOut(id string, chunk []byte) {
 	}
 }
 
+func (s *Session) emitStateChanged(id string, state IdleState) {
+	for _, l := range s.listenersSnapshot() {
+		l.OnChildStateChanged(id, state)
+	}
+}
+
 func (s *Session) ChildEnv() []string {
 	env := os.Environ()
 	// Mark patterm-owned PTYs so a recursive `patterm` invocation can
@@ -374,6 +384,15 @@ func (s *Session) pumpChild(c *Child, runID uint64) {
 				if _, werr := em.Write(chunk); werr != nil {
 					logf("emulator.Write(child %s): %v", c.ID, werr)
 				}
+				// OSC 0/2 title updates ride on the same byte stream as
+				// the rest of the output. Polling the emulator after each
+				// Write is cheap (one cgo call returning a borrowed
+				// string) and lets the classifier treat title changes as
+				// an activity signal — even when the title isn't visible
+				// in the rendered grid.
+				if t, terr := em.Title(); terr == nil {
+					c.recordTitle(t)
+				}
 			}
 			c.recordWrite(chunk)
 			s.emitPTYOut(c.ID, chunk)