Fix cursor positioning, resize, and paste; add App tests and Cursor rules

- Use CoreGraphics (core-graphics crate) for global mouse position instead
  of Tauri's window-relative cursor_position() which fails when hidden
- Switch to titleBarStyle overlay with hiddenTitle for native resize handles
  while keeping the frameless look (decorations:false had no resize affordance)
- Fix paste_and_refocus: use .output() instead of .spawn() so osascript
  actually completes, increase delay to 250ms for reliable app refocus
- Add comprehensive App.test.tsx (7 integration tests) bringing total to 47
- Add multi-select and type badge tests for ClipboardList and ContextMenu
- Update Tauri mock in setup.ts with innerSize/scaleFactor for resize tests
- Create .cursor/rules/ with 4 rule files for project conventions
- Add npm run lint and npm run check scripts
- Update README with full usage table and current test counts (74 total)

Co-authored-by: Cursor <cursoragent@cursor.com>

src-tauri/Cargo.lock

@@ -418,6 +418,19 @@ version = "0.8.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "773648b94d0e5d620f64f280777445740e61fe701025087ec8b57f45c791888b"
 
+[[package]]
+name = "core-graphics"
+version = "0.24.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fa95a34622365fa5bbf40b20b75dba8dfa8c94c734aea8ac9a5ca38af14316f1"
+dependencies = [
+ "bitflags 2.11.1",
+ "core-foundation",
+ "core-graphics-types",
+ "foreign-types",
+ "libc",
+]
+
 [[package]]
 name = "core-graphics"
 version = "0.25.0"
@@ -1948,6 +1961,7 @@ dependencies = [
  "arboard",
  "base64 0.22.1",
  "chrono",
+ "core-graphics 0.24.0",
  "dirs 5.0.1",
  "hex",
  "log",
@@ -3276,7 +3290,7 @@ dependencies = [
  "bitflags 2.11.1",
  "block2",
  "core-foundation",
- "core-graphics",
+ "core-graphics 0.25.0",
  "crossbeam-channel",
  "dbus",
  "dispatch2",