🔒 [security fix] Remove unsafe path canonicalization in directory gate (#111)

* 🔒 [security fix] Remove unsafe path canonicalization in directory gate

🎯 What:
Removed filesystem-level path canonicalization in the DataDirGate check (`canon_or_raw`).

⚠️ Risk:
An attacker could bypass directory authorization by creating a symlink to an authorized directory, allowing them to redirect arbitrary path reads/writes via TOCTOU (Time-of-Check to Time-of-Use) attacks or misleading unverified paths.

🛡️ Solution:
Replaced `fs::canonicalize` with purely lexical path normalization (resolving `.` and `..` in memory) to ensure strict string match validation without following symlinks. Ensure relative paths with `..` that go above the start are handled securely.

Co-authored-by: Horizontal42 <75383519+Horizontal42@users.noreply.github.com>

* 🔒 [security fix] Remove unsafe path canonicalization in directory gate

🎯 What:
Removed filesystem-level path canonicalization in the DataDirGate check (`canon_or_raw`).

⚠️ Risk:
An attacker could bypass directory authorization by creating a symlink to an authorized directory, allowing them to redirect arbitrary path reads/writes via TOCTOU (Time-of-Check to Time-of-Use) attacks or misleading unverified paths.

🛡️ Solution:
Replaced `fs::canonicalize` with purely lexical path normalization (resolving `.` and `..` in memory) to ensure strict string match validation without following symlinks. Ensure relative paths with `..` that go above the start are handled securely without dropping components incorrectly. Added proper Iterator methods to appease clippy.

Co-authored-by: Horizontal42 <75383519+Horizontal42@users.noreply.github.com>

---------

Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>

src-tauri/src/main.rs

@@ -46,7 +46,25 @@ struct DataDirGate {
 }
 
 fn canon_or_raw(p: &Path) -> PathBuf {
-    fs::canonicalize(p).unwrap_or_else(|_| p.to_path_buf())
+    let mut normalized = PathBuf::new();
+    for component in p.components() {
+        match component {
+            std::path::Component::ParentDir => {
+                let can_pop = matches!(
+                    normalized.components().next_back(),
+                    Some(std::path::Component::Normal(_))
+                );
+                if can_pop {
+                    normalized.pop();
+                } else if !normalized.has_root() {
+                    normalized.push(component);
+                }
+            }
+            std::path::Component::CurDir => {}
+            _ => normalized.push(component),
+        }
+    }
+    normalized
 }
 
 /// Exact match against an authorized folder, compared canonicalized so a