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/input-echo-test.mjs

@@ -96,7 +96,7 @@ async function main() {
   page.on('console', msg => consoleLogs.push(`[${msg.type()}] ${msg.text()}`));
 
   try {
-    console.log('Opening Claudeman...');
+    console.log('Opening Codeman...');
     await page.goto(BASE);
     await page.waitForSelector('.xterm-screen', { timeout: 10000 });
     await page.waitForTimeout(2000);