PyCForge 1.3.26 — Conversion diagnostics quick view

Behavior
- A separate amber warning-triangle button sits beside the Tools control.
- It stays visible but disabled until a current rejected/failed conversion has Diagnostics records.
- The dropdown contains those same records: severity, code, module/line and message. It does not generate additional findings.
- Click a row or use keyboard selection and Enter to open its module and highlight its source span.
- Long rows are elided, with their full text in tooltips. Long lists use the native menu scrolling behavior within a bounded popup.
- Diagnostics lacking a source location remain readable but cannot jump to an invented location.
- Editing either source view immediately closes the dropdown and disables the button, before the delayed source synchronization.
- Undoing an edit does not revive the old result. A new failed conversion provides fresh rows.
- Renaming/closing source, changing companion source or starting another conversion disables the old result. Switching tabs alone preserves valid navigation.
- A successful conversion disables the error shortcut.
- The Diagnostics tab and existing Tools/Python-scan behavior are preserved.

Freshness checks
- Navigation is bound to the failed request sequence, source revision, bundle fingerprint and diagnostic collection.
- It does not use the saved-output fingerprint, which can belong to an older successful conversion.
- Source identity and current editor contents are checked before navigation and again after deferred tab projection.

Verification performed
- 40 Qt UI tests passed: 15 new diagnostics cases plus 25 existing Tools and Python-scan interaction tests.
- 17 diagnostics tests passed at 150% Qt display scaling, including large-list scrolling and diagnostics without source locations.
- Tests include typing before source sync, undo, repeated conversions, a prior successful conversion, tab switching, renaming/closing a source, split-editor edits, companion edits, an edit racing deferred navigation and Unicode offsets.
- The long-list presentation test supplies 30 diagnostic records against a real source revision because the converter can stop at its first rejection.
- Disabled/enabled button states and dropdown rendering were visually inspected.
- Converter, Python checker and other package modules outside the UI/version/help changes are byte-identical to v1.3.25.
- Tests used Linux Qt offscreen; native Windows interaction remains for user verification.

Windows check
1. Launch v1.3.26. Confirm a separate gray warning-triangle button beside Tools.
2. Convert source that produces an error. The triangle should become amber and enabled.
3. Open its dropdown. Compare its rows with the Diagnostics tab.
4. Click a row and confirm the correct module and reported source are highlighted.
5. Edit the source. The dropdown should close and its button should disable immediately.
6. Undo the edit. It should stay disabled until another conversion.
7. Repeat after switching tabs and editing in Split Python View.
8. Convert corrected source successfully. The shortcut should be disabled.
9. Confirm the normal Tools menu and recent Python-scan dropdown still work independently.

Packaging
No additional application dependencies. Install the single 1.3.26 wheel into the existing PyCForge environment.
