feat(admin): build the AI Policy console (§6) — approved, spec now implemented

New admin tab "AI" (app/(main)/admin/_tabs/ai-policy.tsx): provider-class
toggles, server model allow-list, BYOK provider allow-list, seats/usage
(front-end for the already-real lib/ai/entitlement.ts), retrieval on/off,
consent text + version bump.

Real backend, not cosmetic: AiConsoleConfig persisted via config-manager
(lib/ai/types.ts, ai-policy.json in the CONFIG dir). New GET/PUT
/api/admin/ai/policy. Enforcement wired at every real chokepoint, not just
the picker: /api/ai/server/chat checks classesEnabled.server and the model
allow-list, /api/ai/retrieve checks retrievalEnabled, /api/ai/server/models
filters by allow-list. GET /api/ai/policy folds classesEnabled into the
classes list clients see.

Resolved the spec's 3 open questions as recommended: BYOK allow-list stays
client-side/advisory (wired into ai-assistant-settings.tsx's addProfile),
tier picker stays cosmetic, master aiAssistantEnabled toggle stays in the
existing Policy tab (this tab links to it instead of duplicating it).

Defaults preserve today's behavior exactly (classesEnabled/allowlists all
start empty/null) — turning this on changes nothing until an admin touches it.

app/api/ai/policy/route.ts

@@ -17,14 +17,25 @@ export async function GET() {
   try {
     await configManager.ensureLoaded();
     const policy = configManager.getPolicy();
+    const consoleConfig = configManager.getAiConsoleConfig();
 
-    const classes = [...DEFAULT_AI_ENTITLEMENT.classes];
-    if (process.env.AI_SERVER_BASE_URL) classes.push('server');
+    // A class must be BOTH infra-available AND not explicitly disabled by
+    // the admin console (docs/ADMIN-AI-POLICY-CONSOLE-SPEC.md §6) to reach
+    // users. Missing classesEnabled entries default to allowed, so this
+    // changes nothing until an admin actually touches the console.
+    const classAllowed = (cls: (typeof DEFAULT_AI_ENTITLEMENT.classes)[number]) => consoleConfig.classesEnabled[cls] !== false;
+    const classes: typeof DEFAULT_AI_ENTITLEMENT.classes = [];
+    if (classAllowed('local')) classes.push('local');
+    if (classAllowed('public')) classes.push('public');
+    if (process.env.AI_SERVER_BASE_URL && classAllowed('server')) classes.push('server');
 
     const aiPolicy: AiPolicy = {
       enabled: policy.features.aiAssistantEnabled,
       entitlement: { ...DEFAULT_AI_ENTITLEMENT, classes },
-      publicConsentVersion: null,
+      publicConsentVersion: consoleConfig.consent?.version ?? null,
+      retrievalEnabled: consoleConfig.retrievalEnabled,
+      consent: consoleConfig.consent,
+      publicProviderAllowlist: consoleConfig.publicProviderAllowlist,
     };
 
     return NextResponse.json(aiPolicy, {