feat: Phase 1 — Contract enforcement pipeline

[windoliver]

Context

Parent: #132 (Grove v2 architecture)
Reviews: CEO review (CLEAN), Eng review (CLEAN), Design review (8/10)
PR: #135 (review artifacts)

Problem

The contract schema in contract.ts defines gates, stop conditions, outcome policies, and agent constraints — but createLocalRuntime defaults to parseContract: false, so they're all dormant. enforcing-store.ts only checks rate limits and artifact sizes. contributeOperation validates relation targets and artifact hashes but not scores, gates, or role-kind constraints. Contributions that violate the contract are silently accepted.

Solution

New enforcement-pipeline.ts (decorator pattern wrapping contributeOperation):

grove_contribute → enforcement-pipeline
  ├─ 1. agentConstraints.allowedKinds check
  ├─ 2. agentConstraints.requiredArtifacts check
  ├─ 3. agentConstraints.requiredRelations check
  ├─ 4. Gate evaluation (metric_improves, has_artifact, has_relation, min_reviews, min_score)
  ├─ 5. before_contribute hook (existing, blocking)
  ├─ 6. contributeOperation() (existing store write)
  ├─ 7. after_contribute hook (existing, flag on failure — not rolled back)
  ├─ 8. evaluateStopConditions() (existing in lifecycle.ts, just wired in)
  ├─ 9. Auto outcome derivation → outcomeStore.set()
  ├─ 10. EventBus publish (best-effort, Phase 3)
  └─ 11. Audit log write (best-effort)

~80% is wiring existing code. evaluateStopConditions(), HookRunner, all gate schemas already exist.

Tasks

• Flip parseContract: true by default in runtime.ts:71
• Create enforcement-pipeline.ts as decorator wrapping contributeOperation
• Agent constraint enforcement (allowedKinds, requiredArtifacts, requiredRelations)
• Gate evaluation (5 gate types from contract.ts:GateSchema)
• First contribution auto-passes metric_improves gate (establishes baseline)
• Automatic outcome derivation from contract.outcomePolicy
• Wire evaluateStopConditions() post-contribute (already exists in lifecycle.ts)
• Wire HookRunner before/after contribute hooks
• Workspace mutation constraints (validate git diff against immutablePaths)
• Structured rejection feedback — typed error objects: { rejected, reason, field, hint } (cherry-pick Define contribution manifest schema #1)
• grove contract validate CLI command (cherry-pick Define relation schema and semantics #2)
• grove_contribute --dry-run parameter (cherry-pick Define artifact schema and CAS addressing #3)
• Enforcement pipeline audit log (cherry-pick Define claim lifecycle for swarm coordination #4)
• ~15 unit tests + ~5 integration tests for enforcement pipeline

Key decisions (from reviews)

• Enforcement pipeline lives in new enforcement-pipeline.ts (decorator pattern, like enforcing-store.ts)
• Hook failures flag metadata, not rolled back (contribution persists)
• First contribution auto-passes gates (establishes baseline)
• Stop evaluation is O(n) — acceptable for v2 scale, incremental deferred to swarm
• GROVE.md in immutablePaths (agents can't modify their own constraints)
• EventBus publish is best-effort (DAG is truth)

Depends on

Nothing — this is the foundation. All other phases depend on this.