refactor: consolidate ~70 scattered constants into 6 new config files (phase 6)

Create 6 domain-focused config files in src/config/ to centralize operational
tuning knobs that were scattered across 15+ source files:

- server-timing.ts: SSE batching, state debounce, scheduled runs, error recovery
- auth-config.ts: session TTL, rate limits, hook timeout
- tunnel-config.ts: QR token rotation, tunnel process lifecycle
- terminal-limits.ts: input length, terminal cols/rows, session name
- ai-defaults.ts: AI model string, idle/plan context limits
- team-config.ts: poll interval, cache sizes

Eliminates all cross-file duplicates:
- AI model string: 5 occurrences → 1 (config only)
- STATS_COLLECTION_INTERVAL_MS: 2 → 1
- timeout: 10000 in hooks-config: 6 → 0 (now HOOK_TIMEOUT_MS)
- MAX_TRACKED_AGENTS shadow: removed, imports from map-limits

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/respawn-controller.ts

@@ -53,6 +53,7 @@ import {
 import { RespawnAdaptiveTiming } from './respawn-adaptive-timing.js';
 import { RespawnCycleMetricsTracker } from './respawn-metrics.js';
 import { calculateHealthScore, shouldSkipClear, type HealthInputs } from './respawn-health.js';
+import { AI_CHECK_MODEL, AI_IDLE_CHECK_MAX_CONTEXT, AI_PLAN_CHECK_MAX_CONTEXT } from './config/ai-defaults.js';
 import type {
   RespawnCycleMetrics,
   RespawnAggregateMetrics,
@@ -547,13 +548,13 @@ const DEFAULT_CONFIG: RespawnConfig = {
   autoAcceptPrompts: true, // auto-accept plan mode prompts (not questions)
   autoAcceptDelayMs: 8000, // 8 seconds before auto-accepting
   aiIdleCheckEnabled: true, // use AI to confirm idle state
-  aiIdleCheckModel: 'claude-opus-4-5-20251101',
-  aiIdleCheckMaxContext: 16000, // ~4k tokens
+  aiIdleCheckModel: AI_CHECK_MODEL,
+  aiIdleCheckMaxContext: AI_IDLE_CHECK_MAX_CONTEXT,
   aiIdleCheckTimeoutMs: 90000, // 90 seconds (thinking can be slow)
   aiIdleCheckCooldownMs: 180000, // 3 minutes after WORKING verdict
   aiPlanCheckEnabled: true, // use AI to confirm plan mode before auto-accept
-  aiPlanCheckModel: 'claude-opus-4-5-20251101',
-  aiPlanCheckMaxContext: 8000, // ~2k tokens (plan mode UI is compact)
+  aiPlanCheckModel: AI_CHECK_MODEL,
+  aiPlanCheckMaxContext: AI_PLAN_CHECK_MAX_CONTEXT,
   aiPlanCheckTimeoutMs: 60000, // 60 seconds (thinking can be slow)
   aiPlanCheckCooldownMs: 30000, // 30 seconds after NOT_PLAN_MODE
   stuckStateDetectionEnabled: true, // detect stuck states