feat(#91): IMP-91 u2~u15 multi-mdx regression CI suite + status-board auto-update

- u2~u5: tests/integration/test_multi_mdx_regression.py — MDX_SET=(01..05)
  cached integration runs + status/structural/visual snapshots +
  full_mdx_coverage assertion (9 snapshots populated for 01-05).
- u6~u11: F0 normalize / F1 V4 ranking / F2 slot_payload /
  F3 classifier-only AI / F4 layout / F5 final.html axis per MDX_SET.
- u12: pyproject.toml — pytest-json-report>=1.5 in dev extras.
- u13: .github/workflows/multi-mdx-regression.yml — pytest+artifact CI.
- u14: scripts/update_status_board.py + tests/scripts/test_update_status_board.py
  — idempotent JSON marker updater (3 unit tests pass).
- u15: PHASE-Z-PIPELINE-STATUS-BOARD.md — 30 F0-F5 × mdx01-05 markers
  initialized `?` + workflow wiring.

Stage 4 verify: 59/59 PASS targeted (smoke 6 + updater 3 + integration 50),
386/386 PASS regression umbrella, 0 failures.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/integration/__snapshots__/final_html.json

@@ -0,0 +1,88 @@
+{
+  "_doc": "IMP-91 u11 — F5 final.html extraction axis. Pin step13_render.json metadata (step_status / pipeline_path_connected / render_inputs.zones_count / render_inputs.layout_preset / slide_title|footer non-empty / final_html_size_bytes) AND structural markers extracted from the on-disk final.html (HTML <title>, slide root count, slide-footer presence, data-zone-position/data-template-id topology). The HTML-extracted zone topology MUST match the step12 slot_payload (position, template_id) sequence already pinned in slot_payload.json (u8) — Jinja2 renders from step12, not step09, so step12 is the correct upstream parity source (step09 selection vs step12 __empty__ collapse is intentional per IMP-87 honesty gate and surfaces in u8). Drift between final.html and slot_payload = render pipeline disconnect. on-disk final.html size_bytes MUST equal step13's reported final_html_size_bytes (byte parity = no truncation / no double-write race).",
+  "01": {
+    "step13_status": "done",
+    "step13_pipeline_path_connected": true,
+    "render_inputs_zones_count": 2,
+    "render_inputs_layout_preset": "horizontal-2",
+    "render_inputs_slide_title_nonempty": true,
+    "render_inputs_slide_footer_nonempty": true,
+    "html_title_matches_render_input": true,
+    "html_slide_root_count": 1,
+    "html_slide_footer_present": true,
+    "html_zone_count": 2,
+    "html_zone_topology": [
+      {"position": "top", "template_id": "bim_dx_comparison_table"},
+      {"position": "bottom", "template_id": "construction_bim_three_usage"}
+    ],
+    "final_html_size_matches_step13_reported": true
+  },
+  "02": {
+    "step13_status": "done",
+    "step13_pipeline_path_connected": true,
+    "render_inputs_zones_count": 2,
+    "render_inputs_layout_preset": "horizontal-2",
+    "render_inputs_slide_title_nonempty": true,
+    "render_inputs_slide_footer_nonempty": true,
+    "html_title_matches_render_input": true,
+    "html_slide_root_count": 1,
+    "html_slide_footer_present": true,
+    "html_zone_count": 2,
+    "html_zone_topology": [
+      {"position": "top", "template_id": "construction_goals_three_circle_intersection"},
+      {"position": "bottom", "template_id": "__empty__"}
+    ],
+    "final_html_size_matches_step13_reported": true
+  },
+  "03": {
+    "step13_status": "done",
+    "step13_pipeline_path_connected": true,
+    "render_inputs_zones_count": 2,
+    "render_inputs_layout_preset": "vertical-2",
+    "render_inputs_slide_title_nonempty": true,
+    "render_inputs_slide_footer_nonempty": true,
+    "html_title_matches_render_input": true,
+    "html_slide_root_count": 1,
+    "html_slide_footer_present": true,
+    "html_zone_count": 2,
+    "html_zone_topology": [
+      {"position": "left", "template_id": "three_parallel_requirements"},
+      {"position": "right", "template_id": "process_product_two_way"}
+    ],
+    "final_html_size_matches_step13_reported": true
+  },
+  "04": {
+    "step13_status": "done",
+    "step13_pipeline_path_connected": true,
+    "render_inputs_zones_count": 3,
+    "render_inputs_layout_preset": "top-1-bottom-2",
+    "render_inputs_slide_title_nonempty": true,
+    "render_inputs_slide_footer_nonempty": true,
+    "html_title_matches_render_input": true,
+    "html_slide_root_count": 1,
+    "html_slide_footer_present": true,
+    "html_zone_count": 3,
+    "html_zone_topology": [
+      {"position": "top", "template_id": "bim_issues_quadrant_four"},
+      {"position": "bottom-left", "template_id": "__empty__"},
+      {"position": "bottom-right", "template_id": "__empty__"}
+    ],
+    "final_html_size_matches_step13_reported": true
+  },
+  "05": {
+    "step13_status": "done",
+    "step13_pipeline_path_connected": true,
+    "render_inputs_zones_count": 1,
+    "render_inputs_layout_preset": "single",
+    "render_inputs_slide_title_nonempty": true,
+    "render_inputs_slide_footer_nonempty": true,
+    "html_title_matches_render_input": true,
+    "html_slide_root_count": 1,
+    "html_slide_footer_present": true,
+    "html_zone_count": 1,
+    "html_zone_topology": [
+      {"position": "primary", "template_id": "__empty__"}
+    ],
+    "final_html_size_matches_step13_reported": true
+  }
+}