feat(mma): Implement track-scoped state persistence and configure sub-agents

.gemini/policies/mma_headless.toml

@@ -0,0 +1,22 @@
+[[rule]]
+toolName = [
+  "read_file",
+  "write_file",
+  "replace",
+  "list_directory",
+  "glob",
+  "grep_search",
+  "search_files",
+  "get_file_summary",
+  "google_web_search",
+  "web_fetch",
+  "codebase_investigator",
+  "cli_help",
+  "activate_skill",
+  "run_shell_command",
+  "run_powershell",
+  "discovered_tool_run_powershell"
+]
+decision = "allow"
+priority = 900
+description = "Allow all MMA tools for sub-agents in headless mode."