feat: WP-0004 T01-T04 — stable corpus, ADRs, regression test

- corpus/markidocx-docs/manifest.yaml: specs as live markidocx project (FR-1101)
- corpus/markidocx-docs/known-drift.md: documented structural drift
- workflows.py: release-regression accepts manifest path; emits corpus_id (FR-1109)
- tests/regression/test_corpus_regression.py: corpus regression suite (FR-1102–1110)
- architecture/ADR-002: python-docx as conversion engine
- architecture/ADR-003: manifest YAML schema
- workplans/MRKD-WP-0004: T01–T04 done; T05 blocked (SBOM path mapping needed)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

corpus/markidocx-docs/manifest.yaml

@@ -0,0 +1,17 @@
+project:
+  name: markidocx-docs
+  feature_level: level1
+  family: article
+
+sources:
+  - path: ../../specs/MarkiDocxProductRequirementsDocument_v0.1.md
+  - path: ../../specs/MarkiDocxFunctionalRequirementsSpecification_v0.2.md
+  - path: ../../specs/MarkiDocxUseCaseCatalog_v0.1.md
+
+output:
+  dir: ./dist
+
+metadata:
+  title: markidocx — Product Documentation
+  author: Markitect Project
+  date: "2026-03-16"