fix: Finding selection support navigate to source file for findings without code flows

[ddrpa]

When a SARIF finding has no codeFlows (common for pattern-match rules like hardcoded credentials or stacktrace-printing), clicking it in the Findings tree does not navigate the code panel to the finding's source file. The editor stays on whatever file was previously selected.

Changes

• Add line?: number to Finding
• Parse locations[0].physicalLocation.region.startLine into finding.line
• Include finding.file in the referenced set alongside flow-step files
• Add f?.file ?? before get().activeFile
• When pathDecorations is empty but finding.line exists, scroll to and highlight the primary line

[misonijnik]

@ddrpa Thanks for fixing that!