VS Code extension finding positions can drift after backend restart

[mesrikanthreddy]

Problem

Noted as a known limitation in `vscode-extension/README.md`:

Findings are keyed by line number only — if the backend restarts mid-edit, positions may shift until the next scan.

If the backend restarts (crash, manual `kshield start` re-run, machine sleep/wake) while a file has unsaved edits since the last scan, existing diagnostic squiggles can point at the wrong line until the next save-triggered scan.

Proposed fix

Options to evaluate:

• Re-scan automatically on backend-reconnect (status bar already detects reachability — could trigger a scan when it transitions from unreachable → reachable)
• Track content hash per diagnostic and invalidate/gray out stale findings if the document has changed since the finding was computed, rather than leaving stale line numbers