feat(confidence-engine): stabilize user-directed investigation flow

Intentional changes in this checkpoint:
- Deconstruct route: use body.targetNodeId (client identity) over raw.model-invented ID
- ThreadContributionsBadge: compact per-thread contribution indicator with expandable history
- Reopen continuation: resume from accumulated contributions instead of reformulating
- showEvidenceLimit gate: hide evidence-limit card during active investigation paths
- Evidence-limit visibility correction in rendering pipeline
- Section ordering: assumptions and connections after 'Still unclear' in focused result
- Prompt v0.3: preserve user-stated alternatives as separate unknowns; no count inflation
- 3 durable regression tests (target identity, contribution persistence, reopen state)
- evidence-limit card visibility gate test suite

Temporary residue removed:
- test-analysis.mjs (scratch diagnostic)
- 5 diagnostic console.log blocks from reasoning-workspace.jsx

prompts/reconstruct-v0.3.md

@@ -16,10 +16,13 @@ You are a neutral analyst performing evidence-based situation reconstruction.
    evidence source, proposed action.
 5. Identify meaningful differences (e.g., some succeed while others fail; revenue rises while cash falls).
 6. Keep multiple plausible interpretations separate where the evidence does not distinguish them.
-7. Distinguish: what was said / what it may mean / why it may have been said.
-8. If input is too ambiguous or contains no useful operational anchors, say so and ask for
+7. When the user explicitly names multiple distinct possible explanations, causes, constraints, or dependencies for the situation, preserve those user-stated alternatives as separate importantUnknowns when they can sensibly be investigated independently. Do not collapse them into one "which factor", "relative contribution", or equivalent umbrella unknown. Do not turn a user-stated possibility into an asserted plausible interpretation — preserve its uncertain status. Only split concepts when the user has presented materially distinct dimensions that each warrant independent investigation.
+8. Distinguish: what was said / what it may mean / why it may have been said.
+9. If input is too ambiguous or contains no useful operational anchors, say so and ask for
    the single piece of context that would best distinguish plausible interpretations.
 
+10. Do not split concepts merely to increase the number of unknowns — only separate when the user has presented materially distinct dimensions worth independent investigation.
+
 ## Normalisation and rate reasoning (apply whenever applicable)
 
 When the scenario mentions counts, totals, frequencies, or volumes alongside changes in