Add README, plugin citations, and multi-platform release CI.

Ship screenshots and third-party notices for the desktop shell, and
package Windows, macOS, deb, rpm, and Flatpak from GitHub Releases.

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

.gitignore

@@ -0,0 +1,27 @@
+# Python helpers (scripts/, tests/)
+__pycache__/
+*.py[cod]
+*.egg-info/
+
+# Rust / Cargo
+/target/
+**/*.rs.bk
+*.pdb
+
+# Tauri generated schemas
+src-tauri/gen/
+
+# Vendored dsh, ModLens, presets (make vendor)
+/vendor/
+
+# Packaging
+/dist/
+/build/
+*.flatpak
+.flatpak-build/
+.flatpak-builder/
+.flatpak-repo/
+
+# OS
+.DS_Store
+*~