v0.3-T1 — ahc validate (with budget sanity check)

[sv-pro]

Summary

Implement ahc validate <manifest> — the first v0.3 toolchain command. Validates a World Manifest v2 file for schema correctness and budget coherence without compiling or running anything.

Depends on: #120 (v0.2 Phase 4 compiler integration)

Scope

• Schema-level validation: required fields, type checks, cross-reference integrity, unknown action detection
• Budget sanity check: declared budgets must cover at least one known model in the pricing registry
• Clear, actionable error messages with field paths
• Exit code 0 on success, non-zero on validation failure

Key Files

• src/agent_hypervisor/compiler/cli.py — add validate command
• src/agent_hypervisor/compiler/schema_v2.py — validation logic
• tests/compiler/test_validate.py — new test file

Acceptance Criteria

• ahc validate manifests/workspace_v2.yaml exits 0
• ahc validate on a malformed manifest prints actionable errors and exits non-zero
• Budget sanity check fires when no model in pricing registry matches declared budget
• pytest tests/compiler/test_validate.py -v passes

Milestone

v0.3