delete ProcessTracker — replaced by ActiveToolCall + KillOnDrop

All process management now goes through active_tools:
- TUI reads metadata (name, elapsed time)
- Ctrl+K aborts handles (KillOnDrop sends SIGTERM)
- Running count from active_tools.len()

No more separate PID tracking, register/unregister, or
ProcessInfo. One data structure for everything.

Co-Developed-By: Kent Overstreet <kent.overstreet@linux.dev>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

src/subconscious/api.rs

@@ -9,7 +9,7 @@
 
 use crate::user::api::ApiClient;
 use crate::user::types::*;
-use crate::agent::tools::{self as agent_tools, ProcessTracker, ToolOutput};
+use crate::agent::tools::{self as agent_tools};
 
 use std::sync::OnceLock;
 
@@ -55,7 +55,6 @@ pub async fn call_api_with_tools(
             .filter(|t| tools.iter().any(|w| w == &t.function.name))
             .collect()
     };
-    let tracker = ProcessTracker::new();
     // Provenance tracks which agent:phase is making writes.
     // Updated between steps by the bail function via set_provenance().
     let first_phase = phases.first().map(|s| s.as_str()).unwrap_or("");
@@ -175,7 +174,7 @@ pub async fn call_api_with_tools(
                 };
 
                 let prov = provenance.borrow().clone();
-                let output = match agent_tools::dispatch_shared(&call.function.name, &args, &tracker, Some(&prov)).await {
+                let output = match agent_tools::dispatch_shared(&call.function.name, &args, Some(&prov)).await {
                     Some(out) => out,
                     None => ToolOutput::error(format!("Unknown tool: {}", call.function.name)),
                 };