tools: each module exports only tool() or tools(), nothing else

Every tool module now has a clean interface:
- read, write, edit, grep, glob, bash, vision: pub fn tool() -> Tool
- web: pub fn tools() -> [Tool; 2]
- memory: pub fn memory_tools() -> Vec<Tool>
- channels: pub fn tools() -> Vec<Tool>
- control: pub fn tools() -> Vec<Tool>

Definition and handler functions are private to each module.
mod.rs::tools() just chains the module exports.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/agent/tools/write.rs

@@ -13,7 +13,11 @@ struct Args {
     content: String,
 }
 
-pub fn definition() -> ToolDef {
+pub fn tool() -> super::Tool {
+    super::Tool { def: definition(), handler: |_a, v| Box::pin(async move { write_file(&v) }) }
+}
+
+fn definition() -> ToolDef {
     ToolDef::new(
         "write_file",
         "Write content to a file. Creates the file if it doesn't exist, \
@@ -35,7 +39,7 @@ pub fn definition() -> ToolDef {
     )
 }
 
-pub fn write_file(args: &serde_json::Value) -> Result<String> {
+fn write_file(args: &serde_json::Value) -> Result<String> {
     let args: Args = serde_json::from_value(args.clone())
         .context("invalid write_file arguments")?;