chore(openspec): drop 9 superseded proposals + 11 stub archive files

Drop 9 batch proposals that are superseded by the boocode-lift-analysis
(boocontext-audit, conductor upgrades, self-healing/verify-gate skills):
add-3tier-memory, import-llm-evaluator, import-pregel-engine, plugin-platform,
conductor-evolution, code-intelligence-upgrade, dev-workflow, ui-overhaul,
agent-reliability.

Delete 11 stub archive files (49-66B each, 'Status: Shipped. Archived.' only)
that provide zero documentation value over the existing CHANGELOG.md + git tags.

openspec/changes/archived/2026-06-07-hybrid-workflow-engine/specs/workflow-lifecycle/spec.md

@@ -0,0 +1,51 @@
+## ADDED Requirements
+
+### Requirement: Run states
+A workflow run SHALL transition through states: `pending → running → completed | failed | cancelled`. It MAY transition to `paused` for approval gates.
+
+#### Scenario: Normal completion
+- **WHEN** all DAG nodes complete successfully
+- **THEN** the run status SHALL be `completed`
+
+#### Scenario: Node failure
+- **WHEN** a node fails and no retry succeeds
+- **THEN** the run status SHALL be `failed`
+
+#### Scenario: User cancellation
+- **WHEN** a user cancels a running workflow
+- **THEN** the run status SHALL be `cancelled`
+
+#### Scenario: Approval pause
+- **WHEN** an approval node is reached
+- **THEN** the run status SHALL transition to `paused`
+- **THEN** it SHALL transition back to `running` on approval
+
+### Requirement: Resume from failure
+A failed workflow SHALL support resumption, skipping already-completed nodes using stored outputs from the event log.
+
+#### Scenario: Resume skips completed nodes
+- **WHEN** a failed workflow has 2 completed nodes out of 5
+- **THEN** resuming SHALL skip nodes 1-2 and re-execute from node 3
+
+#### Scenario: Resume with always_run
+- **WHEN** a node has `always_run: true` and the workflow is resumed
+- **THEN** the node SHALL re-execute even if it completed previously
+
+### Requirement: Event-based observability
+All lifecycle transitions SHALL emit typed events through the event emitter for observability and external subscribers.
+
+#### Scenario: Events for every state transition
+- **WHEN** a workflow starts
+- **THEN** a `workflow_started` event SHALL be emitted
+- **WHEN** a workflow completes
+- **THEN** a `workflow_completed` event SHALL be emitted
+- **WHEN** a node starts/completes/fails/skips
+- **THEN** corresponding node events SHALL be emitted
+
+### Requirement: Cleanup
+The engine SHALL support cleaning up old workflow runs and their artifacts.
+
+#### Scenario: Cleanup by age
+- **WHEN** cleanup is invoked with a retention period (default 7 days)
+- **THEN** runs older than the retention period SHALL have their artifacts removed
+- **THEN** run records MAY be pruned from the store