Add sats-denominated bounty and claim fields to forge issues #78

Outcome

Attach a Bitcoin bounty and claim lifecycle to an issue without creating a second work record or paying for presence.

Current behavior

The treasury and self-custodial MoneyDevKit wallet stack exist, but tracker issues have no price, claim, verifier, or payout state. The current API extension work in #35 provides the governed place for OpenAgents-specific fields.

Source: docs/episode-triage.md, episodes 224, 225, 235, 237, and the settlement station.

Contract

• Add a discoverable openagents.bounty issue extension with amount in sats, funding source, currency, claim state, claimant, expiry, verification policy, and payout receipt reference.
• Keep issue state, project status, work-job state, claim state, and payment state separate.
• Support unpriced, open, claimed, submitted, verified, paid, canceled, and expired outcomes with explicit transitions.
• Require repository authority to price work and claimant identity to claim it.
• Bind verification to the exact accepted-outcome evidence and revision.
• Use the self-custodial treasury path; do not add hosted user custody.
• Refuse presence, token volume, online time, or narration as payout evidence.

Acceptance criteria

• One issue can expose its bounty state through web and API without breaking GitHub-shaped clients.
• Concurrent claims produce one winner or a visible policy result.
• Changing scope after a claim invalidates or re-accepts the exact priced specification.
• A verified result cannot be paid twice.
• Cancel, expire, dispute, and unauthorized cases preserve an audited history.

Verification

Test extension discovery, lifecycle transitions, concurrent claims, scope fingerprints, authority, idempotency, disputes, and compatibility. Run mix precommit.

Dependencies

Depends on #35 and the accepted-outcome and exact-receipt issues in project 3.