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/harness/runner.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"regexp"
 	"strings"
+	"time"
 )
 
 type Event struct {
@@ -175,6 +176,41 @@ func runStep(s *Session, step Step, results map[string]json.RawMessage) error {
 			return fmt.Errorf("no saved result %q", step.From)
 		}
 		return assertJSONValue(raw, step.Path, step.Equals, step.Contains, step.AllowSubstring)
+	case "wait_until_mcp":
+		// Poll an MCP method until the assertion at Path holds (or
+		// Contains substring matches), or TimeoutMS elapses. Used by the
+		// idle-detection scenarios to wait for a child's idle_state to
+		// reach a target value without sprinkling sleeps.
+		params, perr := resolveParams(step.Params, results)
+		if perr != nil {
+			return perr
+		}
+		deadline := time.Now().Add(timeoutMS(step.TimeoutMS))
+		var lastRaw json.RawMessage
+		var lastErr error
+		for {
+			raw, err := s.MCPCall(step.Method, params)
+			if err == nil {
+				if aerr := assertJSONValue(raw, step.Path, step.Equals, step.Contains, step.AllowSubstring); aerr == nil {
+					if step.SaveAs != "" {
+						results[step.SaveAs] = raw
+					}
+					return nil
+				} else {
+					lastErr = aerr
+					lastRaw = raw
+				}
+			} else {
+				lastErr = err
+			}
+			if time.Now().After(deadline) {
+				if lastErr != nil {
+					return fmt.Errorf("wait_until_mcp timeout: %w (last response: %s)", lastErr, string(lastRaw))
+				}
+				return fmt.Errorf("wait_until_mcp timeout (no successful call)")
+			}
+			time.Sleep(100 * time.Millisecond)
+		}
 	}
 	return fmt.Errorf("unknown step type %q", step.Type)
 }