feat(mcp): enforce spec-compliant tool registry

- Reject dotted tool identifiers during registration and remove alias-backed lookups.
- Drop web.search compatibility, normalize all code/tests around the canonical web_search name, and update consent/session logic.
- Harden CLI toggles to manage the spec-compliant identifier and ensure MCP configs shed non-compliant entries automatically.

Acceptance Criteria:
- Tool registry denies invalid identifiers by default and no alias codepaths remain.

Test Notes:
- cargo check -p owlen-core (tests unavailable in sandbox).

crates/owlen-cli/tests/agent_tests.rs

@@ -9,6 +9,7 @@
 
 use owlen_cli::agent::{AgentConfig, AgentExecutor, LlmResponse};
 use owlen_core::mcp::remote_client::RemoteMcpClient;
+use owlen_core::tools::WEB_SEARCH_TOOL_NAME;
 use std::sync::Arc;
 
 #[tokio::test]
@@ -27,7 +28,7 @@ async fn test_react_parsing_tool_call() {
             arguments,
         }) => {
             assert_eq!(thought, "I should search for information");
-            assert_eq!(tool_name, "web_search");
+            assert_eq!(tool_name.as_str(), WEB_SEARCH_TOOL_NAME);
             assert_eq!(arguments["query"], "rust async programming");
         }
         other => panic!("Expected ToolCall, got: {:?}", other),