fix: peer review — 5 correctness bugs across who, db, lock, embedding, main

Comprehensive peer code review identified and fixed the following:

1. who.rs: @-prefixed path routing used `target` (with @) instead of
   `clean` (stripped) when checking for '/' and passing to Expert mode,
   causing `lore who @src/auth/` to silently return zero results because
   the SQL LIKE matched against `@src/auth/%` which never exists.

2. db.rs: After ROLLBACK TO savepoint on migration failure, the savepoint
   was never RELEASEd, leaving it active on the connection. Fixed in both
   run_migrations() and run_migrations_from_dir().

3. lock.rs: Multiple acquire() calls (e.g. re-acquiring a stale lock)
   replaced the heartbeat_handle without stopping the old thread, causing
   two concurrent heartbeat writers competing on the same lock row. Now
   signals the old thread to stop and joins it before spawning a new one.

4. chunk_ids.rs: encode_rowid() had no guard for chunk_index >= 1000
   (CHUNK_ROWID_MULTIPLIER), which would cause rowid collisions between
   adjacent documents. Added range assertion [0, 1000).

5. main.rs: Fallback JSON error formatting in handle_auth_test
   interpolated LoreError Display output without escaping quotes or
   backslashes, potentially producing malformed JSON for robot-mode
   consumers. Now escapes both characters before interpolation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/cli/commands/who.rs

@@ -54,9 +54,9 @@ fn resolve_mode<'a>(args: &'a WhoArgs) -> Result<WhoMode<'a>> {
         // Disambiguation: if target contains '/', it's a file path.
         // GitLab usernames never contain '/'.
         // Root files (no '/') require --path.
-        if target.contains('/') {
+        if clean.contains('/') {
             return Ok(WhoMode::Expert {
-                path: normalize_repo_path(target),
+                path: normalize_repo_path(clean),
             });
         }
         return Ok(WhoMode::Workload { username: clean });

src/core/db.rs

@@ -140,6 +140,7 @@ pub fn run_migrations(conn: &Connection) -> Result<()> {
             }
             Err(e) => {
                 let _ = conn.execute_batch(&format!("ROLLBACK TO {}", savepoint_name));
+                let _ = conn.execute_batch(&format!("RELEASE {}", savepoint_name));
                 return Err(LoreError::MigrationFailed {
                     version,
                     message: e.to_string(),
@@ -216,6 +217,7 @@ pub fn run_migrations_from_dir(conn: &Connection, migrations_dir: &Path) -> Resu
             }
             Err(e) => {
                 let _ = conn.execute_batch(&format!("ROLLBACK TO {}", savepoint_name));
+                let _ = conn.execute_batch(&format!("RELEASE {}", savepoint_name));
                 return Err(LoreError::MigrationFailed {
                     version,
                     message: e.to_string(),

src/core/lock.rs

@@ -135,6 +135,13 @@ impl AppLock {
     }
 
     fn start_heartbeat(&mut self) {
+        // Stop any existing heartbeat thread before starting a new one
+        if let Some(handle) = self.heartbeat_handle.take() {
+            self.released.store(true, Ordering::SeqCst);
+            let _ = handle.join();
+            self.released.store(false, Ordering::SeqCst);
+        }
+
         let name = self.name.clone();
         let owner = self.owner.clone();
         let interval = Duration::from_millis(self.heartbeat_interval_ms);

src/embedding/chunk_ids.rs

@@ -1,6 +1,10 @@
 pub const CHUNK_ROWID_MULTIPLIER: i64 = 1000;
 
 pub fn encode_rowid(document_id: i64, chunk_index: i64) -> i64 {
+    assert!(
+        (0..CHUNK_ROWID_MULTIPLIER).contains(&chunk_index),
+        "chunk_index {chunk_index} out of range [0, {CHUNK_ROWID_MULTIPLIER})"
+    );
     document_id
         .checked_mul(CHUNK_ROWID_MULTIPLIER)
         .and_then(|v| v.checked_add(chunk_index))

src/main.rs

@@ -1217,7 +1217,12 @@ async fn handle_auth_test(
                 eprintln!(
                     "{}",
                     serde_json::to_string(&output).unwrap_or_else(|_| {
-                        format!(r#"{{"error":{{"code":"{}","message":"{}"}}}}"#, e.code(), e)
+                        let msg = e.to_string().replace('\\', "\\\\").replace('"', "\\\"");
+                        format!(
+                            r#"{{"error":{{"code":"{}","message":"{}"}}}}"#,
+                            e.code(),
+                            msg
+                        )
                     })
                 );
             } else {