[walid-baharwal]

Changes

• Restore developer-tool PATH for packaged GUI launches and use the platform's shell consistently.
• Run native tests and package builds on Linux, Windows, Intel macOS, and Apple Silicon macOS.
• Build DEB, RPM, AppImage, NSIS EXE, and ad hoc signed DMG installers; validate Linux package installation and AppImage extraction.
• Fix Fedora RPM dependency names and document installation, signing limits, and desktop smoke checks.

Local checks

• pnpm build and pnpm test:frontend pass.
• cargo test --manifest-path src-tauri/Cargo.toml --no-default-features --locked passes.
• pnpm format:check and actionlint pass.
• Native Fedora build needs missing WebKitGTK and D-Bus development packages on the host. The PR matrix will run native builds on all target operating systems.