Add beta supportability follow-up

[daredoole]

Summary

• add machine-readable diagnostics summary.json to the beta bundle
• extend doctor with Wayland/uinput and Secret Service/session-bus hints
• add a beta bug-report issue template covering Linux session, Windows/PowerToys version, monitor topology, auth source, and clipboard mode
• update beta workflow docs to use the diagnostics bundle path

Compatibility context

This builds on the current MWB-compatible implementation. It does not change protocol behavior or topology semantics. It adds supportability for the compatibility matrix we need to track: Linux X11/Wayland sessions, /dev/uinput access, Secret Service/key_file/inline key modes, Windows PowerToys Mouse Without Borders versions, monitor layouts including AAB/BAA/ABA/stacked/asymmetric, and clipboard helper availability.

Validation

• bash -n scripts/inputflow-diagnostics-bundle.sh
• bash -n mwb-desktop-ui.sh
• bash -n scripts/validate-rpm-packaging.sh
• python3 YAML parse for .github/ISSUE_TEMPLATE/bug_report.yml
• scripts/validate-rpm-packaging.sh
• cmake --build build --target mwb_client mwb_tray -j2
• ctest --test-dir build -R 'mwb_client_doctor|mwb_input_latency_tests|mwb_input_device_capability_tests' --output-on-failure
• diagnostics bundle smoke test with summary.json validation