feat(mcp): add Antigravity, fix Gemini http/sse shape, report unsupported CLIs

Formats verified against real agy/gemini/codex mcp add output.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

src/config/cli-registry/schema.ts

@@ -386,7 +386,7 @@ const capabilitiesSchema = z
           .max(100)
           .regex(/^[A-Za-z0-9._-]+(\/[A-Za-z0-9._-]+)*$/)
           .refine((v) => !v.split('/').includes('..'), 'must not contain ..'),
-        format: z.enum(['claude-json', 'gemini-json', 'codex-toml', 'opencode-json']),
+        format: z.enum(['claude-json', 'gemini-json', 'codex-toml', 'opencode-json', 'antigravity-json']),
       })
       .strict()
       .optional(),

src/config/cli-registry/stock.ts

@@ -804,6 +804,7 @@ const ANTIGRAVITY: CliEntry = {
     // Like codex: an ABSENT config already defaults safe (no bypass flag), so only a
     // SENT config needs the flag forced off — nothing is materialized.
     privilegedParams: [{ param: 'dangerouslySkipPermissions', clampTo: false }],
+    mcpConfig: { path: '.gemini/config/mcp_config.json', format: 'antigravity-json' },
     // No known CLI/env/config mechanism — Antigravity's own docs describe a GUI-only
     // custom-endpoint setting and explicitly say it "cannot currently" become the core
     // reasoning model. Toolbar entry stays disabled for this mode.

src/config/cli-registry/types.ts

@@ -517,7 +517,10 @@ export interface CliCapabilities {
    * adapter reads and writes. Absent = no known/verified MCP config file, so the CLI is
    * skipped by sync rather than guessed at.
    */
-  mcpConfig?: { path: string; format: 'claude-json' | 'gemini-json' | 'codex-toml' | 'opencode-json' };
+  mcpConfig?: {
+    path: string;
+    format: 'claude-json' | 'gemini-json' | 'codex-toml' | 'opencode-json' | 'antigravity-json';
+  };
   /**
    * How this CLI is pointed at a user-supplied custom OpenAI-compatible
    * endpoint (local, e.g. llama.cpp, or cloud, e.g. Azure AI Foundry) — the