Credit system: 45-day decay, DRF accounting, and caliber redemption

[jeremymanning]

Description

Per spec Phase 11 (T129) and whitepaper, the credit system needs:

1. 45-day half-life decay: credits decay with minimum floor protection (trailing_30d_earn_rate * 30)
2. DRF dominant-dimension accounting: multi-dimensional credit computation (compute, memory, storage, network)
3. Caliber-class redemption matching: redemption jobs placed on hardware at or above earned class
4. Anti-hoarding: if outstanding credits exceed 110% of trailing redemption demand, decay rate increases

Requirements

• Implement CreditDecay LedgerEntry type
• Decay runs on configurable schedule (default: daily)
• Floor protection prevents active donors from losing all credits
• DRF accounting tracks 4 dimensions per credit event
• Caliber matching enforced at scheduler level
• Anti-hoarding mechanism adjusts decay rate dynamically

Success Criteria

• Credits decay at 45-day half-life rate
• Floor protection preserves minimum balance for active donors
• DRF accounting correctly identifies dominant resource dimension
• Redemption jobs match caliber class
• Anti-hoarding mechanism activates above 110% threshold
• Integration tests with realistic credit scenarios
• cargo test passes

Testing (Principle V)

• Simulate 90 days of credit earn/spend → verify decay curve matches 45-day half-life
• Active donor with floor protection → verify minimum balance preserved
• Submit redemption job at C3 caliber → verify placed on C3+ hardware only
• Simulate hoarding scenario → verify increased decay rate activates

[jeremymanning]

Addressed in spec 004-full-implementation (PR #59). Implementation verified in code; 802 tests passing across Linux/macOS/Windows. See #57 master plan for full context.