feat: remove proxyMode — all traffic goes through mcplocal proxy

proxyMode "direct" was a security hole (leaked secrets as plaintext env
vars in .mcp.json) and bypassed all mcplocal features (gating, audit,
RBAC, content pipeline, namespacing). Removed from schema, API, CLI,
and all tests. Old configs with proxyMode are accepted but silently
stripped via Zod .transform() for backward compatibility.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/db/tests/models.test.ts

@@ -506,23 +506,16 @@ describe('ProjectServer', () => {
 // ── Project new fields ──
 
 describe('Project new fields', () => {
-  it('defaults proxyMode to direct', async () => {
-    const project = await createProject();
-    expect(project.proxyMode).toBe('direct');
-  });
-
-  it('stores proxyMode, llmProvider, llmModel', async () => {
+  it('stores llmProvider, llmModel', async () => {
     const user = await createUser();
     const project = await prisma.project.create({
       data: {
         name: 'filtered-project',
         ownerId: user.id,
-        proxyMode: 'filtered',
         llmProvider: 'gemini-cli',
         llmModel: 'gemini-2.0-flash',
       },
     });
-    expect(project.proxyMode).toBe('filtered');
     expect(project.llmProvider).toBe('gemini-cli');
     expect(project.llmModel).toBe('gemini-2.0-flash');
   });