poc-hook: call memory-search internally on UserPromptSubmit

Spawn memory-search --hook as a subprocess, piping the hook input
JSON through stdin and printing its stdout. This ensures memory
context injection goes through the same hook whose output Claude
Code reliably persists, fixing the issue where memory-search as a
separate hook had its output silently dropped.

Co-Authored-By: ProofOfConcept <poc@bcachefs.org>

poc-memory/src/bin/poc-hook.rs

@@ -151,6 +151,28 @@ fn main() {
         "UserPromptSubmit" => {
             signal_user();
             check_notifications();
+
+            // Run memory-search, passing through the hook input it needs
+            if let Ok(output) = Command::new("memory-search")
+                .arg("--hook")
+                .stdin(std::process::Stdio::piped())
+                .stdout(std::process::Stdio::piped())
+                .stderr(std::process::Stdio::null())
+                .spawn()
+                .and_then(|mut child| {
+                    if let Some(ref mut stdin) = child.stdin {
+                        use std::io::Write;
+                        let _ = stdin.write_all(input.as_bytes());
+                    }
+                    child.wait_with_output()
+                })
+            {
+                let text = String::from_utf8_lossy(&output.stdout);
+                if !text.is_empty() {
+                    print!("{text}");
+                }
+            }
+
             if let Some(ref t) = transcript {
                 check_context(t, false);
             }