Decouple sidecar versioning from app versioning

Sidecar now has its own version (1.0.0) and release lifecycle:
- Sidecar tags: sidecar-v1.0.0, sidecar-v1.0.1, etc.
- App tags: v0.2.x (unchanged)
- Sidecar workflow triggers only on python/** changes or manual dispatch
- App release no longer bumps python/pyproject.toml

Sidecar version tracked via sidecar-version.txt in app data dir:
- resolve_sidecar_path() reads version from file instead of CARGO_PKG_VERSION
- download_sidecar() fetches latest sidecar-v* release from Gitea API
- check_sidecar_update() compares local vs remote sidecar versions
- Version file written after successful download

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

src-tauri/src/sidecar/mod.rs

@@ -56,10 +56,33 @@ impl SidecarManager {
         cfg!(debug_assertions) || std::env::var("VOICE_TO_NOTES_DEV").is_ok()
     }
 
+    /// Read the locally installed sidecar version from `sidecar-version.txt`.
+    fn read_sidecar_version() -> Result<String, String> {
+        let data_dir = DATA_DIR.get().ok_or("App data directory not initialized")?;
+        let version_file = data_dir.join("sidecar-version.txt");
+        std::fs::read_to_string(&version_file)
+            .map_err(|_| {
+                "Sidecar not installed: sidecar-version.txt not found. Please download the sidecar."
+                    .to_string()
+            })
+            .map(|v| v.trim().to_string())
+            .and_then(|v| {
+                if v.is_empty() {
+                    Err(
+                        "Sidecar version file is empty. Please re-download the sidecar."
+                            .to_string(),
+                    )
+                } else {
+                    Ok(v)
+                }
+            })
+    }
+
     /// Resolve the frozen sidecar binary path (production mode).
     ///
-    /// First checks if the sidecar is already extracted to the app data directory.
-    /// If not, looks for `sidecar.zip` in the Tauri resource directory and extracts it.
+    /// Reads the installed sidecar version from `sidecar-version.txt` and
+    /// looks for the binary in the corresponding `sidecar-{version}` directory.
+    /// If the version file doesn't exist, the sidecar hasn't been downloaded yet.
     fn resolve_sidecar_path() -> Result<PathBuf, String> {
         let binary_name = if cfg!(target_os = "windows") {
             "voice-to-notes-sidecar.exe"
@@ -67,16 +90,15 @@ impl SidecarManager {
             "voice-to-notes-sidecar"
         };
 
-        // Versioned extraction directory prevents stale sidecar after app updates
         let data_dir = DATA_DIR.get().ok_or("App data directory not initialized")?;
-        let current_version = env!("CARGO_PKG_VERSION");
+        let current_version = Self::read_sidecar_version()?;
         let extract_dir = data_dir.join(format!("sidecar-{}", current_version));
 
         let binary_path = extract_dir.join(binary_name);
 
         // Already extracted — use it directly
         if binary_path.exists() {
-            Self::cleanup_old_sidecars(data_dir, current_version);
+            Self::cleanup_old_sidecars(data_dir, &current_version);
             return Ok(binary_path);
         }
 
@@ -102,7 +124,7 @@ impl SidecarManager {
             }
         }
 
-        Self::cleanup_old_sidecars(data_dir, current_version);
+        Self::cleanup_old_sidecars(data_dir, &current_version);
         Ok(binary_path)
     }