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/subagent-watcher.ts

@@ -13,7 +13,7 @@ import { homedir } from 'node:os';
 import { join, basename } from 'node:path';
 import { execFile } from 'node:child_process';
 import { readFile, readdir, stat as statAsync } from 'node:fs/promises';
-import { PENDING_TOOL_CALL_TTL_MS, MAX_PENDING_TOOL_CALLS } from './config/map-limits.js';
+import { PENDING_TOOL_CALL_TTL_MS, MAX_PENDING_TOOL_CALLS, MAX_TRACKED_AGENTS } from './config/map-limits.js';
 import { CleanupManager, KeyedDebouncer } from './utils/index.js';
 
 // ========== Types ==========
@@ -134,7 +134,6 @@ const FILE_ALIVE_THRESHOLD_MS = 30000; // File mtime within 30s = agent alive (p
 const STALE_COMPLETED_MAX_AGE_MS = 60 * 60 * 1000; // Remove completed agents older than 1 hour
 const STALE_IDLE_MAX_AGE_MS = 4 * 60 * 60 * 1000; // Remove idle agents older than 4 hours
 const STARTUP_MAX_FILE_AGE_MS = 4 * 60 * 60 * 1000; // Only load files modified in last 4 hours on startup
-const MAX_TRACKED_AGENTS = 500; // Maximum agents to track (LRU eviction when exceeded)
 
 // Internal Claude Code agent patterns to filter out (not real user-initiated subagents)
 const INTERNAL_AGENT_PATTERNS = [