Fix: reap stale agent pid files in poc-hook

scan_pid_files was removed as dead code but it was actually needed
by the hook path — the bug was that it was never wired in. Add
reap_agent_pids() directly to poc-hook.rs and call it on every
UserPromptSubmit. Kills timed-out agents (10min) and cleans up
pid files for dead processes.

Also remove dead subconscious/subconscious.rs (420 lines) — was
forked to claude/agent_cycles.rs and never removed.

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

src/claude/poc-hook.rs

@@ -83,6 +83,46 @@ fn check_notifications() {
     }
 }
 
+/// Check for stale agent processes in a state dir.
+/// Cleans up pid files for dead processes and kills timed-out ones.
+fn reap_agent_pids(state_dir: &std::path::Path, timeout_secs: u64) {
+    let Ok(entries) = fs::read_dir(state_dir) else { return };
+    for entry in entries.flatten() {
+        let name = entry.file_name();
+        let name_str = name.to_string_lossy();
+        let Some(pid_str) = name_str.strip_prefix("pid-") else { continue };
+        let Ok(pid) = pid_str.parse::<i32>() else { continue };
+
+        if unsafe { libc::kill(pid, 0) } != 0 {
+            fs::remove_file(entry.path()).ok();
+            continue;
+        }
+
+        if timeout_secs > 0 {
+            if let Ok(meta) = entry.metadata() {
+                if let Ok(modified) = meta.modified() {
+                    if modified.elapsed().unwrap_or_default().as_secs() > timeout_secs {
+                        unsafe { libc::kill(pid, libc::SIGTERM); }
+                        fs::remove_file(entry.path()).ok();
+                    }
+                }
+            }
+        }
+    }
+}
+
+/// Reap all agent output directories.
+fn reap_all_agents() {
+    let agent_output = poc_memory::store::memory_dir().join("agent-output");
+    if let Ok(entries) = fs::read_dir(&agent_output) {
+        for entry in entries.flatten() {
+            if entry.file_type().map_or(false, |t| t.is_dir()) {
+                reap_agent_pids(&entry.path(), 600); // 10 min timeout
+            }
+        }
+    }
+}
+
 /// Check if enough new conversation has accumulated to trigger an observation run.
 fn maybe_trigger_observation(transcript: &PathBuf) {
     let cursor_file = poc_memory::store::memory_dir().join("observation-cursor");
@@ -189,6 +229,7 @@ fn main() {
         "UserPromptSubmit" => {
             signal_user();
             check_notifications();
+            reap_all_agents();
             print!("{}", poc_memory::memory_search::run_hook(&input));
 
             if let Some(ref t) = transcript {