tools: static string definitions, no runtime JSON construction

Tool definitions are now &'static str (name, description,
parameters_json) instead of runtime-constructed serde_json::Value.
No more json!() macro, no more ToolDef::new() for tool definitions.

The JSON schema strings are written directly as string literals.
When sent to the API, they can be interpolated without
serialization/deserialization.

Multi-tool modules return fixed-size arrays instead of Vecs:
- memory: [Tool; 12], journal: [Tool; 3]
- channels: [Tool; 4]
- control: [Tool; 3]
- web: [Tool; 2]

ToolDef/FunctionDef remain for backward compat (API wire format,
summarize_args) but are no longer used in tool definitions.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

src/claude/mcp-server.rs

@@ -70,9 +70,9 @@ fn notify(method: &str, params: Value) {
 fn tool_definitions() -> Vec<Value> {
     poc_memory::agent::tools::tools().into_iter()
         .map(|t| json!({
-            "name": t.def.function.name,
-            "description": t.def.function.description,
-            "inputSchema": t.def.function.parameters,
+            "name": t.name,
+            "description": t.description,
+            "inputSchema": serde_json::from_str::<Value>(t.parameters_json).unwrap_or(json!({})),
         }))
         .collect()
 }
@@ -81,7 +81,7 @@ fn tool_definitions() -> Vec<Value> {
 
 fn dispatch_tool(name: &str, args: &Value) -> Result<String, String> {
     let tools = poc_memory::agent::tools::tools();
-    let tool = tools.iter().find(|t| t.def.function.name == name);
+    let tool = tools.iter().find(|t| t.name == name);
     let Some(tool) = tool else {
         return Err(format!("unknown tool: {name}"));
     };