feat(confidence-engine): v0.59a — correct Investigation revision provenance

Semantic revision tracking ensures every meaningful persisted
Investigation change advances investigationRevision exactly once,
while Report generation records (but does not advance) the current
revision as generatedFromRevision for provenance integrity.

Corrections:
- updateFindingDisposition: add setInvestigationRevision(+1) for
  semantic transitions (eligible→not_relevant, restore)
- updateFindingProposition: add no-op guard + setInvestigationRevision(+1)
- onRestart/ContinueLaterBanner/reset button: add setInvestigationRevision(0)
- onSituationGraphChange (Re-open seam): already had revision +1 in dirty impl

Established behaviour preserved:
- Re-open via reopenResolvedUnknown → onSituationGraphChange → revision +1
- Empty Done via handleDoneForNowPromotion → revision +1
- Report generation records generatedFromRevision, advances by 0
- Autosave passes revision but does not increment it
- clearInvestigation() ownership intact

Tests: targeted Vitest suite (17 tests) covering all provenance boundaries.

Durable rule documented in current-handoff.md §v0.59a.

app/investigations/[id]/report/page.jsx

@@ -48,10 +48,12 @@ export default function ReportPage() {
 
         const data = await res.json();
         if (data.success) {
-          setExisting((prev) => {
-            const updated = { ...prev, investigationReport: { understanding: data.understanding, plausibleInterpretations: data.plausibleInterpretations, hasPlausibleInterpretations: true } };
-            saveInvestigation(updated);
-            return updated;
+          /* ── v0.59a — provenance: record generation revision (does NOT change Investigation revision) ── */
+          const rev = existing?.investigationRevision ?? 0;
+          const reportData = { understanding: data.understanding, plausibleInterpretations: data.plausibleInterpretations, hasPlausibleInterpretations: true, generatedFromRevision: rev };
+          setExisting((p) => {
+            saveInvestigation({ ...p, investigationReport: reportData });
+            return { ...p, investigationReport: reportData };
           });
         } else {
           setGenerationError(true);