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/scenarios/timer_pause_resume.json

@@ -0,0 +1,62 @@
+{
+  "name": "timer_pause_resume",
+  "presets": {
+    "processes": [
+      {
+        "name": "echoer",
+        "argv": ["sh", "-lc", "while read line; do echo \"saw:$line\"; done"]
+      }
+    ]
+  },
+  "trust": ["echoer"],
+  "steps": [
+    {
+      "type": "mcp_call",
+      "method": "spawn_process",
+      "params": {"kind": "command", "preset": "echoer", "name": "echoer"},
+      "save_as": "proc"
+    },
+    { "type": "wait_stable", "timeout_ms": 1500 },
+    {
+      "type": "mcp_call",
+      "method": "timer_set",
+      "params": {
+        "seconds": 1,
+        "body": "after-resume",
+        "owner_process_id": "{{proc.process_id}}"
+      },
+      "save_as": "tmr"
+    },
+    {
+      "type": "mcp_call",
+      "method": "timer_pause",
+      "params": {"timer_id": "{{tmr.timer_id}}"}
+    },
+    {
+      "type": "mcp_call",
+      "method": "timer_list",
+      "params": {"owner_process_id": "{{proc.process_id}}"},
+      "save_as": "listed"
+    },
+    {
+      "type": "assert_saved",
+      "from": "listed",
+      "path": "0.status",
+      "equals": "paused"
+    },
+    {
+      "type": "mcp_call",
+      "method": "timer_resume",
+      "params": {"timer_id": "{{tmr.timer_id}}"}
+    },
+    {
+      "type": "wait_until_mcp",
+      "method": "get_process_output",
+      "params": {"process_id": "{{proc.process_id}}", "mode": "grid"},
+      "path": "content",
+      "contains": "saw:after-resume",
+      "allow_substring": true,
+      "timeout_ms": 5000
+    }
+  ]
+}