chore(openspec): drop 9 superseded proposals + 11 stub archive files

Drop 9 batch proposals that are superseded by the boocode-lift-analysis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

@@ -0,0 +1,34 @@
+## ADDED Requirements
+
+### Requirement: SOP markdown as secondary format
+Workflows MAY be defined as `.sop.md` files in addition to YAML. The engine SHALL detect `.sop.md` files during discovery and transpile them to the DAG node representation.
+
+#### Scenario: SOP file discovered alongside YAML
+- **WHEN** a `.sop.md` file exists in the workflows directory alongside `.yaml` workflow files
+- **THEN** both SHALL be discovered and listed as available workflows
+
+#### Scenario: SOP transpiled to prompt nodes
+- **WHEN** a `.sop.md` file is loaded
+- **THEN** each `## Steps` section item SHALL become a `prompt:` node
+- **THEN** `## Parameters` SHALL be extracted as node metadata
+
+### Requirement: RFC 2119 constraint extraction
+The transpiler SHALL extract RFC 2119 constraints from `**Constraints:**` blocks and embed them in the prompt text of the corresponding node.
+
+#### Scenario: Constraints included in prompt
+- **WHEN** a step has `**Constraints:** - You MUST do X`
+- **THEN** the constraint text SHALL be appended to the node's prompt
+
+### Requirement: Overview as workflow description
+The `## Overview` section of a `.sop.md` file SHALL become the workflow's `description` field.
+
+#### Scenario: Overview maps to description
+- **WHEN** a `.sop.md` has `## Overview\nThis SOP does X`
+- **THEN** the resulting workflow SHALL have `description: "This SOP does X"`
+
+### Requirement: Parameter acquisition constraints
+The transpiler SHALL validate that all required parameters from `## Parameters` are present before execution, using the constraint pattern from the SOP.
+
+#### Scenario: Missing required parameter
+- **WHEN** a required parameter has no value provided
+- **THEN** the workflow SHALL prompt the user for the missing parameter before executing