Schema + viewer: carry claim falsification criteria and render claim proof/deps

[EYH0602]

Background

Gap analysis vs the deployed ara-hub viewer (https://www.agenticresearch.sh/ara/AmberLJC/ara-paperbench/artifacts/speedrun/nanogpt-speedrun). This is a schema-widening task (parser + manifest + viewer), not viewer-only.

Problem

Falsification is the core epistemic payload of an ARA claim, but it is lost at compile time:

1. Claim (crates/ara-core/src/manifest.rs:366-375) has no falsification field — the hub's claim cards render a "falsification" criterion per claim (e.g. C01: "If any record fails to achieve val_loss ≤ 3.28, or if the cumulative speedup is substantially less than 16×."). Our viewer can never show this.
2. Fields we do parse are also dropped in the detail pane: ClaimView (crates/ara-viewer/src/detail.rs:143-158) keeps only title/statement/status. proof refs (E##) and claim→claim deps never render.
3. The claim id itself is not shown on the card.

Proposal

• Widen the claims parser + Claim to carry falsification (optional string).
• Render full claim cards in the detail pane: id, title, statement, status pill, falsification ("refuted if…"), proof refs, and dependency chips.

Acceptance

• falsification parsed from logic/claims.md and present in the manifest
• Claim cards show id, falsification, proof refs, and deps when present
• Unknown/absent fields degrade gracefully (current rendering)
• Parser + viewer unit tests