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/agent/tools/bash.rs

@@ -8,11 +8,10 @@
 
 use anyhow::{Context, Result};
 use serde::Deserialize;
-use serde_json::json;
 use std::process::Stdio;
 use tokio::io::AsyncReadExt;
 
-use super::{ToolDef, default_timeout};
+use super::default_timeout;
 
 /// RAII guard that SIGTERMs the process group on drop.
 /// Ensures child processes are cleaned up when a task is aborted.
@@ -34,29 +33,12 @@ struct Args {
 }
 
 pub fn tool() -> super::Tool {
-    super::Tool { def: definition(), handler: |_a, v| Box::pin(async move { run_bash(&v).await }) }
-}
-
-fn definition() -> ToolDef {
-    ToolDef::new(
-        "bash",
-        "Execute a bash command and return its output. \
-         Use for git operations, building, running tests, and other terminal tasks.",
-        json!({
-            "type": "object",
-            "properties": {
-                "command": {
-                    "type": "string",
-                    "description": "The bash command to execute"
-                },
-                "timeout_secs": {
-                    "type": "integer",
-                    "description": "Timeout in seconds (default 120)"
-                }
-            },
-            "required": ["command"]
-        }),
-    )
+    super::Tool {
+        name: "bash",
+        description: "Execute a bash command and return its output. Use for git operations, building, running tests, and other terminal tasks.",
+        parameters_json: r#"{"type":"object","properties":{"command":{"type":"string","description":"The bash command to execute"},"timeout_secs":{"type":"integer","description":"Timeout in seconds (default 120)"}},"required":["command"]}"#,
+        handler: |_a, v| Box::pin(async move { run_bash(&v).await }),
+    }
 }
 
 async fn run_bash(args: &serde_json::Value) -> Result<String> {