chore: rename Claudeman to Codeman

Full product rename across 109 files (~834 occurrences):
- Env vars: CLAUDEMAN_* → CODEMAN_*
- Data dirs: ~/.claudeman/ → ~/.codeman/, ~/claudeman-cases/ → ~/codeman-cases/
- tmux prefix: claudeman- → codeman-
- localStorage: claudeman-* → codeman-*
- Package/CLI: claudeman → codeman
- GitHub repo: Ark0N/Claudeman → Ark0N/Codeman
- systemd service: claudeman-web → codeman-web
- Class: ClaudemanApp → CodemanApp

Migration infrastructure for seamless transition:
- state-store.ts: auto-migrates data directories on startup
- tmux-manager.ts: dual-prefix detection (legacy claudeman- sessions)
- app.js: localStorage key migration (preserves old keys)

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

test/perf-subagent-load.test.ts

@@ -1,5 +1,5 @@
 /**
- * Performance tests: Claudeman responsiveness under subagent load
+ * Performance tests: Codeman responsiveness under subagent load
  *
  * Measures event loop lag caused by:
  * 1. SubagentWatcher processing many agent files simultaneously
@@ -112,7 +112,7 @@ describe('SubagentWatcher performance', () => {
   let projectsDir: string;
 
   beforeEach(() => {
-    tmpDir = mkdtempSync(join(tmpdir(), 'claudeman-perf-'));
+    tmpDir = mkdtempSync(join(tmpdir(), 'codeman-perf-'));
     projectsDir = join(tmpDir, 'projects');
     mkdirSync(projectsDir, { recursive: true });
   });