tools: delete ToolDef and FunctionDef

ToolDef and FunctionDef are gone. Tool definitions are static strings
on the Tool struct. The API layer builds JSON from Tool::to_json().

- ChatRequest.tools is now Option<serde_json::Value>
- start_stream takes &[Tool] instead of Option<&[ToolDef]>
- openai::stream_events takes &serde_json::Value for tools
- memory_and_journal_tools() returns Vec<Tool> for subconscious agents
- Subconscious agents filter by t.name instead of t.function.name

No more runtime JSON construction for tool definitions.
No more ToolDef::new(). No more FunctionDef.

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

src/agent/api/mod.rs

@@ -17,7 +17,7 @@ use std::time::{Duration, Instant};
 
 use tokio::sync::mpsc;
 
-use crate::agent::tools::{ToolCall, ToolDef, FunctionCall};
+use crate::agent::tools::{self as agent_tools, ToolCall, FunctionCall};
 use crate::user::ui_channel::{UiMessage, UiSender};
 
 /// A JoinHandle that aborts its task when dropped.
@@ -41,6 +41,12 @@ pub struct SamplingParams {
 //  Stream events — yielded by backends, consumed by the runner
 // ─────────────────────────────────────────────────────────────
 
+/// Build the tools JSON string from a slice of Tools.
+fn tools_to_json_str(tools: &[agent_tools::Tool]) -> String {
+    let inner: Vec<String> = tools.iter().map(|t| t.to_json()).collect();
+    format!("[{}]", inner.join(","))
+}
+
 /// Events produced by the streaming API backends.
 /// The runner reads these and decides what to display where.
 pub enum StreamEvent {
@@ -98,7 +104,7 @@ impl ApiClient {
     pub fn start_stream(
         &self,
         messages: &[Message],
-        tools: Option<&[ToolDef]>,
+        tools: &[agent_tools::Tool],
         ui_tx: &UiSender,
         reasoning_effort: &str,
         sampling: SamplingParams,
@@ -109,7 +115,8 @@ impl ApiClient {
         let api_key = self.api_key.clone();
         let model = self.model.clone();
         let messages = messages.to_vec();
-        let tools = tools.map(|t| t.to_vec());
+        let tools_json = tools_to_json_str(tools);
+        let tools_value: serde_json::Value = serde_json::from_str(&tools_json).unwrap_or_default();
         let ui_tx = ui_tx.clone();
         let reasoning_effort = reasoning_effort.to_string();
         let base_url = self.base_url.clone();
@@ -117,7 +124,7 @@ impl ApiClient {
         let handle = tokio::spawn(async move {
             let result = openai::stream_events(
                 &client, &base_url, &api_key, &model,
-                &messages, tools.as_deref(), &tx, &ui_tx,
+                &messages, &tools_value, &tx, &ui_tx,
                 &reasoning_effort, sampling, priority,
             ).await;
             if let Err(e) = result {
@@ -131,7 +138,7 @@ impl ApiClient {
     pub async fn chat_completion_stream_temp(
         &self,
         messages: &[Message],
-        tools: Option<&[ToolDef]>,
+        tools: &[agent_tools::Tool],
         ui_tx: &UiSender,
         reasoning_effort: &str,
         sampling: SamplingParams,