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/grep.rs

@@ -23,7 +23,11 @@ struct Args {
 
 fn default_path() -> String { ".".into() }
 
-pub fn definition() -> ToolDef {
+pub fn tool() -> super::Tool {
+    super::Tool { def: definition(), handler: |_a, v| Box::pin(async move { grep(&v) }) }
+}
+
+fn definition() -> ToolDef {
     ToolDef::new(
         "grep",
         "Search for a pattern in files. Returns matching file paths by default, \
@@ -64,7 +68,7 @@ fn has_rg() -> bool {
     *HAS_RG.get_or_init(|| Command::new("rg").arg("--version").output().is_ok())
 }
 
-pub fn grep(args: &serde_json::Value) -> Result<String> {
+fn grep(args: &serde_json::Value) -> Result<String> {
     let a: Args = serde_json::from_value(args.clone())
         .context("invalid grep arguments")?;