Fix double-prefix sidecar dir and stale PID lock on startup

Two bugs preventing sidecar from starting:

1. Directory was "sidecar-sidecar-v1.0.3" (double prefix) because
   sidecar_dir_for_version() prepended "sidecar-" to a version that
   already contained it. Now uses the tag directly as the dir name.

2. After a crash, the Python InstanceLock PID file at
   ~/.local-transcription/app.lock remained, blocking the next launch
   with "Another instance is already running". Now clears the stale
   lock file before spawning the sidecar.

Also fixed cleanup_old_versions() and tests to match the corrected
directory naming.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src-tauri/src/sidecar/mod.rs

@@ -54,7 +54,8 @@ fn read_installed_version() -> Option<String> {
 }
 
 fn sidecar_dir_for_version(version: &str) -> PathBuf {
-    data_dir().join(format!("sidecar-{version}"))
+    // version is the full tag name, e.g. "sidecar-v1.0.3" -- use it directly
+    data_dir().join(version)
 }
 
 fn binary_path_for_version(version: &str) -> PathBuf {
@@ -371,12 +372,12 @@ fn extract_zip(zip_path: &std::path::Path, dest: &std::path::Path) -> Result<(),
 
 fn cleanup_old_versions(current_version: &str) {
     let data = data_dir();
-    let current_dir_name = format!("sidecar-{current_version}");
+    // current_version is already the full tag, e.g. "sidecar-v1.0.3"
     if let Ok(entries) = std::fs::read_dir(data) {
         for entry in entries.flatten() {
             let name = entry.file_name().to_string_lossy().to_string();
-            if name.starts_with("sidecar-v")      // e.g. sidecar-v1.0.1
+            if name.starts_with("sidecar-")
-                && name != current_dir_name
+                && name != current_version
                 && entry.path().is_dir()
             {
                 let _ = std::fs::remove_dir_all(entry.path());
@@ -433,6 +434,20 @@ impl SidecarManager {
                 .ok_or_else(|| "Sidecar running but port unknown".into());
         }
 
+        // Clear stale PID lock from a previous crash so the sidecar can start.
+        // The Python InstanceLock writes to ~/.local-transcription/app.lock
+        if let Ok(home) = std::env::var("USERPROFILE")
+            .or_else(|_| std::env::var("HOME"))
+        {
+            let lock_file = PathBuf::from(home)
+                .join(".local-transcription")
+                .join("app.lock");
+            if lock_file.exists() {
+                eprintln!("[sidecar] Removing stale lock file: {}", lock_file.display());
+                let _ = std::fs::remove_file(&lock_file);
+            }
+        }
+
         let is_dev = cfg!(debug_assertions)
             || std::env::var("LOCAL_TRANSCRIPTION_DEV")
                 .map(|v| v == "1")
@@ -791,7 +806,7 @@ mod tests {
     fn sidecar_dir_for_version_contains_version() {
         let data = ensure_dirs_initialised();
         let dir = sidecar_dir_for_version("sidecar-v1.2.3");
-        assert_eq!(dir, data.join("sidecar-sidecar-v1.2.3"));
+        assert_eq!(dir, data.join("sidecar-v1.2.3"));
     }
 
     #[test]
@@ -836,9 +851,8 @@ mod tests {
             std::fs::create_dir_all(data.join(d)).unwrap();
         }
 
-        // cleanup_old_versions builds `current_dir_name = "sidecar-{version}"`.
+        // current_version is the full tag, e.g. "sidecar-v1.0.2"
-        // Passing "v1.0.2" produces "sidecar-v1.0.2" which matches our dir name.
+        cleanup_old_versions("sidecar-v1.0.2");
-        cleanup_old_versions("v1.0.2");
 
         assert!(
             !data.join("sidecar-v1.0.0").exists(),