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-core/tests/agent_tool_flow.rs

@@ -2,6 +2,7 @@ use std::{any::Any, collections::HashMap, sync::Arc};
 
 use async_trait::async_trait;
 use futures::StreamExt;
+use owlen_core::tools::{WEB_SEARCH_TOOL_NAME, tool_name_matches};
 use owlen_core::{
     Config, Error, Mode, Provider,
     config::McpMode,
@@ -88,7 +89,7 @@ impl Provider for StreamingToolProvider {
 
 fn tool_descriptor() -> McpToolDescriptor {
     McpToolDescriptor {
-        name: "web_search".to_string(),
+        name: WEB_SEARCH_TOOL_NAME.to_string(),
         description: "search".to_string(),
         input_schema: serde_json::json!({"type": "object"}),
         requires_network: true,
@@ -123,7 +124,7 @@ impl CachedResponseClient {
         metadata.insert("cached".to_string(), "true".to_string());
 
         let response = McpToolResponse {
-            name: "web_search".to_string(),
+            name: WEB_SEARCH_TOOL_NAME.to_string(),
             success: true,
             output: serde_json::json!({
                 "query": "rust",
@@ -286,13 +287,13 @@ async fn web_tool_timeout_fails_over_to_cached_result() {
     ]);
 
     let call = McpToolCall {
-        name: "web_search".to_string(),
+        name: WEB_SEARCH_TOOL_NAME.to_string(),
         arguments: serde_json::json!({ "query": "rust", "max_results": 3 }),
     };
 
     let response = client.call_tool(call.clone()).await.expect("fallback");
 
-    assert_eq!(response.name, "web_search");
+    assert!(tool_name_matches(&response.name, WEB_SEARCH_TOOL_NAME));
     assert_eq!(
         response.metadata.get("source").map(String::as_str),
         Some("cache")