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>

workplans/MRKD-WP-0004-stable-corpus-architecture.md

@@ -26,7 +26,7 @@ also writes the two deferred architecture decision records and generates the fir
 
 ```task
 id: MRKD-WP-0004-T01
-status: todo
+status: done
 priority: high
 state_hub_task_id: f1a36613-ceaa-4786-ac39-cd3a7fd1c142
 ```
@@ -55,7 +55,7 @@ of the product documentation exists in `corpus/markidocx-docs/dist/`.
 
 ```task
 id: MRKD-WP-0004-T02
-status: todo
+status: done
 priority: high
 state_hub_task_id: f17e959f-28da-4386-9004-b5e036054b06
 ```
@@ -84,7 +84,7 @@ written to `.markidocx/evidence/` and retrievable via CLI.
 
 ```task
 id: MRKD-WP-0004-T03
-status: todo
+status: done
 priority: medium
 state_hub_task_id: bfe2a9fa-25b2-4b4b-b21b-eae457716ce0
 ```
@@ -112,7 +112,7 @@ Deliverable: `architecture/ADR-002-*.md` present and follows ADR-001 conventions
 
 ```task
 id: MRKD-WP-0004-T04
-status: todo
+status: done
 priority: medium
 state_hub_task_id: b6de6733-b332-4efc-9e23-82fce205b856
 ```
@@ -140,7 +140,8 @@ Deliverable: `architecture/ADR-003-*.md` present.
 
 ```task
 id: MRKD-WP-0004-T05
-status: todo
+status: blocked
+blocking_reason: ops-bridge ingest_sbom_tool cannot access /home/tegwick/ paths (runs as worsch). Configure host_paths mapping for marki-docx, then re-run ingest.
 priority: medium
 state_hub_task_id: 36aecd50-8176-4122-9706-a8697d8f5936
 ```