rebrand: sweep remaining switchboard refs + rename cookies/storage keys

- CSS headers (4 files): Switchboard Core → Armature
- Editor .mjs headers (8 files): Chat Switchboard → Armature
- SQL migration comments + seed data (20 files): Switchboard Core → Armature
- Webhook header: X-Switchboard-Event → X-Armature-Event
- Cookie: sb_token → arm_token (3 Go files + auth.js)
- localStorage: sb_auth → arm_auth (auth.js + 2 test runners)
- localStorage: switchboard_theme → armature_theme (theme.js + base.html)
- Debug engine filter: chatSwitchboard/switchboard/sb_ → armatureChat/armature/arm_
- JS export: switchboardTheme → armatureTheme (theme.mjs + code-editor.mjs)

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

server/pages/templates/base.html

@@ -38,10 +38,10 @@
     <meta name="theme-color" content="#0e0e10" id="metaThemeColor">
     <script>
         // Early theme application — prevents flash of wrong theme on all surfaces.
-        // Read from Theme API key (switchboard_theme) as authoritative source.
+        // Read from Theme API key (armature_theme) as authoritative source.
         (function() {
             try {
-                var mode = localStorage.getItem('switchboard_theme') || 'system';
+                var mode = localStorage.getItem('armature_theme') || 'system';
                 var resolved = mode;
                 if (mode === 'system') resolved = window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
                 document.documentElement.setAttribute('data-theme', resolved);