refactor: extract app.js into 6 domain modules with deferred init

Split the monolithic app.js (~12.5K lines) into 6 focused mixin modules
that extend CodemanApp.prototype via Object.assign:

- terminal-ui.js — terminal setup, rendering pipeline, controls
- respawn-ui.js — respawn banner, countdown, presets, run summary
- ralph-panel.js — Ralph state panel, fix_plan, plan versioning
- settings-ui.js — app settings, visibility, web push, tunnel/QR, help
- panels-ui.js — subagent panel, teams, insights, file browser, log viewer
- session-ui.js — quick start, session options, case settings

Fix deferred script init ordering: wrap CodemanApp instantiation in
DOMContentLoaded so all defer'd mixin modules execute their
Object.assign before the constructor runs. Without this, init() calls
methods like applyHeaderVisibilitySettings() that don't exist yet.

Guard missing cleanupWizardDragging() call in subagent-windows.js.
Update build.mjs to minify/hash all new modules. Update CLAUDE.md
with new frontend architecture and load order.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/web/public/subagent-windows.js

@@ -15,7 +15,7 @@
  * @mixin Extends CodemanApp.prototype via Object.assign
  * @dependency app.js (CodemanApp class, this.subagents, this.subagentWindows, this.minimizedSubagents)
  * @dependency constants.js (escapeHtml)
- * @loadorder 9 of 9 — loaded last, after api-client.js
+ * @loadorder 15 of 15 — loaded last, after api-client.js
  */
 
 // Codeman — Subagent window management for CodemanApp
@@ -991,7 +991,7 @@ Object.assign(CodemanApp.prototype, {
     }
 
     // Clean up wizard drag listeners (leak fix: document-level handlers)
-    this.cleanupWizardDragging();
+    if (typeof this.cleanupWizardDragging === 'function') this.cleanupWizardDragging();
 
     // Deactivate focus trap if wizard was open (leak fix: keydown listener)
     if (this.activeFocusTrap) {