perf: implement phase 1-3 performance optimizations

Add implementation plans and code structure analysis for a 3-phase
performance optimization effort. Refactor core modules to reduce
timer overhead, consolidate regex usage, extract exec timeout config,
add debouncer utility, and streamline server/schema validation.

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

src/config/exec-timeout.ts

@@ -0,0 +1,10 @@
+/**
+ * @fileoverview Shared exec timeout constant.
+ *
+ * Used by CLI resolvers and tmux-manager for execSync/exec calls.
+ *
+ * @module config/exec-timeout
+ */
+
+/** Timeout for exec commands (5 seconds) */
+export const EXEC_TIMEOUT_MS = 5000;