[D3-02] Build navigable citation graph from verified paper metadata

[dkritarth]

Outcome

Visualize citation relationships with honest provenance and navigation back to papers/references.

Dependencies

Blocked by #43.

Scope

Define graph data source and confidence before UI. Use local paper references and verified metadata sources; record provenance. Support graph navigation and missing/ambiguous matches. No fabricated edges.

Acceptance criteria

• Every node/edge has source and confidence/match rationale.
• Ambiguous references remain unresolved or user-confirmable.
• Click opens local paper or reference context when available.
• Graph handles isolated nodes, cycles, duplicates, and moderate corpus without freezing.
• Rebuild/update behavior after ingest/trash/purge is deterministic.
• Accessibility has non-visual list/table alternative.

Live verification

Build graph from known related papers, manually validate sampled edges against reference lists, test ambiguous titles/authors, delete/restore paper, inspect performance and keyboard access.

Required evidence

Focused PR uses Closes #44. Provide a written design first, failing tests/baseline, focused/full tests, typecheck, build, diff check, exact live Electron procedure, real-paper evidence, screenshots, console state, performance observations, and limitations. Independent reviewer repeats representative workflow.