Design an incremental scan/report pipeline state machine

[Muawiya-contact]

Goal

Turn the scan/report pipeline into an explicit incremental state machine.

The desktop app can now show provisional findings while scanning, but the final report still has several full passes. A future architecture could make each stage clearer, testable, and easier to stream.

Why this is super advanced

This touches scanner, graph, rules, risk, dedup, report, cancellation, and UI events.

Current pipeline shape:

scanner -> graph -> rules + risk -> dedup -> report

Possible future shape:

enum ScanPipelineEvent {
    EntrySeen(FileEntry),
    ProvisionalFinding(Finding),
    GraphReady,
    FinalFinding(Finding),
    DuplicateSetReady(DuplicateSet),
    Complete(Report),
}

Suggested deliverable

Start with a design PR or markdown document. Do not try to rewrite the whole pipeline in one PR.

Acceptance criteria

• Identifies the pipeline states and what each state owns.
• Keeps cancellation behavior clear.
• Keeps final report authority separate from provisional UI previews.
• Includes a migration plan with small PR steps.