Implement the full correction-checkpoint rollback pipeline:
- Workspace snapshots: CheckpointService.create_workspace_snapshot()
creates diff-based checkpoints before decision execution, storing
only changed file paths in metadata.extra["diff_paths"]
- CorrectionService.revert_decisions(): new high-level entry point
that creates a correction, computes impact, invokes checkpoint
rollback, and archives artifacts in a single call
- Physical artifact archival: CheckpointService.archive_artifacts()
moves files to .cleveragents/archived_artifacts/ instead of just
flagging metadata. CorrectionService._archive_decision_artifacts()
delegates to this during revert execution
- Selective rollback: CheckpointService.selective_rollback() wraps
rollback_to_checkpoint with atomic semantics — captures HEAD before
rollback and recovers on failure
- Diff-based storage: _compute_diff_snapshot() computes changed paths
between checkpoints via git diff; snapshots store diff manifest and
SHA-256 hash in metadata
- CLI: plan rollback now accepts --to-checkpoint <id> in addition to
the positional checkpoint_id argument; uses selective_rollback for
atomic execution
- DI wiring: Container now injects checkpoint_service into
CorrectionService; CLI correct command uses container-provided
service instead of ad-hoc instance (fixes bug #986)
- Checkpoint model: pre_decision added to allowed checkpoint_type
values
- TDD: Removed @tdd_expected_fail from wiring test feature since the
DI bug is now fixed
ISSUES CLOSED: #943
