feat(mcp): implement 4-pillar auto-sync, dynamic introspection, and non-blocking validation

- Pillar 1 (Runtime Auto-Sync):
  * Add sync_agent_tool_schemas() in src/mcp.rs to atomically export live tool schemas & instructions to ~/.gemini/antigravity/mcp/opencadstudio/
  * Automatically invoke sync on MCP startup (mcp::run()) and GUI automation startup (transport::listen())
  * Add --sync-mcp-schemas CLI flag in src/cli.rs and src/main.rs

- Pillar 2 (Development Hook):
  * Strengthen export_agent_tool_schemas test in src/mcp.rs to assert all schema files and instructions.md exist and are in sync on every cargo test run

- Pillar 3 (In-Band Dynamic Introspection):
  * Add 'tools' to READ_OPS in src/mcp.rs and query match in src/app/control/mod.rs
  * Enable agents to dynamically query live tool definitions and instructions via ocs_read (op: 'tools') over MCP or raw socket

- Pillar 4 (Non-Blocking Validation):
  * Set additionalProperties: true on ocs_capture schema in src/mcp.rs to prevent rigid schema rejection of emerging options

src/cli.rs

@@ -80,6 +80,11 @@ pub struct Cli {
     #[arg(help = crate::t!("Connect AI clients to the running editor over MCP stdio.").into_owned(), long_help = None)]
     pub mcp: bool,
 
+    /// Export and synchronize AI agent MCP tool schemas to ~/.gemini/antigravity/mcp/opencadstudio/ and exit.
+    #[arg(long = "sync-mcp-schemas")]
+    #[arg(help = crate::t!("Export and synchronize AI agent MCP tool schemas to ~/.gemini/antigravity/mcp/opencadstudio/ and exit.").into_owned(), long_help = None)]
+    pub sync_mcp_schemas: bool,
+
     /// TCP port for --serve (defaults to stdin/stdout).
     #[arg(long, value_name = "PORT")]
     #[arg(help = crate::t!("TCP port for --serve (defaults to stdin/stdout).").into_owned(), long_help = None)]