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>

docs/browser-testing-guide.md

@@ -1,6 +1,6 @@
-# Browser Testing Guide for Claudeman
+# Browser Testing Guide for Codeman
 
-This guide documents the browser testing infrastructure, framework comparison results, and best practices for testing the Claudeman web UI.
+This guide documents the browser testing infrastructure, framework comparison results, and best practices for testing the Codeman web UI.
 
 ## Quick Start
 
@@ -14,7 +14,7 @@ npm test -- test/browser-e2e.test.ts
 
 ## Framework Comparison Results
 
-We tested three browser automation frameworks against the Claudeman web UI:
+We tested three browser automation frameworks against the Codeman web UI:
 
 | Framework | Avg Duration | Best For |
 |-----------|--------------|----------|
@@ -114,7 +114,7 @@ await page.waitForSelector('.session-tab', { state: 'visible' });
 
 // Assertions with expect
 await expect(page.locator('.header')).toBeVisible();
-await expect(page).toHaveTitle('Claudeman');
+await expect(page).toHaveTitle('Codeman');
 
 await browser.close();
 ```