chore(openspec): drop 9 superseded proposals + 11 stub archive files

Drop 9 batch proposals that are superseded by the boocode-lift-analysis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/library-api/spec.md

@@ -0,0 +1,44 @@
+## ADDED Requirements
+
+### Requirement: Programmatic execution
+The engine SHALL export an `executeWorkflow()` function that accepts a workflow definition, store, and options.
+
+#### Scenario: Execute workflow from code
+- **WHEN** a host application calls `executeWorkflow(workflowDef, store, { userMessage: "..." })`
+- **THEN** the workflow SHALL execute and return a `WorkflowExecutionResult`
+
+### Requirement: Workflow parsing
+The engine SHALL export `parseWorkflow(yaml: string): WorkflowDefinition` and `parseWorkflowFile(path: string): WorkflowDefinition` functions.
+
+#### Scenario: Parse YAML string
+- **WHEN** a host application calls `parseWorkflow(yamlString)`
+- **THEN** it SHALL return a validated `WorkflowDefinition`
+
+#### Scenario: Parse YAML file
+- **WHEN** a host application calls `parseWorkflowFile("./workflows/my-workflow.yaml")`
+- **THEN** it SHALL read and parse the file, returning a validated `WorkflowDefinition`
+
+### Requirement: Workflow discovery
+The engine SHALL export `discoverWorkflows(cwd: string): WorkflowLoadResult` for finding workflows in the filesystem.
+
+#### Scenario: Discover workflows
+- **WHEN** a host application calls `discoverWorkflows(cwd)`
+- **THEN** it SHALL return all discovered workflows from the project's `.archon/workflows/` directory
+
+### Requirement: Store constructors
+The engine SHALL export store constructors for each backend: `createFsStore(path)`, `createSqliteStore(path)`, `createPostgresStore(connectionString)`.
+
+#### Scenario: Create filesystem store
+- **WHEN** a host application calls `createFsStore("./data")`
+- **THEN** it SHALL return an initialized `IWorkflowStore` using the filesystem backend
+
+#### Scenario: Create SQLite store
+- **WHEN** a host application calls `createSqliteStore("./ion.db")`
+- **THEN** it SHALL return an initialized `IWorkflowStore` using SQLite
+
+### Requirement: TypeScript types
+All public APIs SHALL export full TypeScript type definitions.
+
+#### Scenario: Types available
+- **WHEN** a host application imports from the package
+- **THEN** `WorkflowDefinition`, `DagNode`, `NodeOutput`, `WorkflowRun`, `WorkflowExecutionResult`, `IWorkflowStore` types SHALL all be exported