Diagram generation: ref-arch-driven procedure + spec validator + KB enrichment

The diagram path now follows a documented standard procedure (lookup
the closest Oracle Architecture Center reference → confirm components
→ author absolute_layout → spec validator → render → visually verify)
and ships persistent guardrails so layout regressions can't recur.

Persistent procedure changes (apply to all users, all sessions):
- tools/diagram_spec_validator.py — geometry checks (CONTAINER_TOO_THIN,
  CONTAINER_PADDING_VIOLATION, LABEL_OVERFLOW_PARENT) run BEFORE either
  renderer (drawio + PPTX). Catches the subnet-collapse / label-overflow
  bugs that the post-render drawio validator missed.
- tools/oci_diagram_gen.py + tools/oci_pptx_diagram_gen.py — call the
  spec validator before emitting any output. Adds mysql / mysql_heatwave
  type aliases.
- tools/archcenter_pattern_lookup.py — scores against cached page
  descriptions (not just the 1-line summary), supports --queries for
  multi-fragment composition, and applies synonym expansion via
  kb/architecture-center/synonyms.yaml so "LB HA cross AD" matches
  "load balancer high availability availability domain".
- kb/architecture-center/synonyms.yaml — canonical synonym table
  (load balancer, autonomous database, data guard, …) used by the
  lookup scorer.

KB enrichment:
- tools/archcenter_description_fetcher.py + 121 cached _description.md
  under kb/diagram/assets/archcenter-refs/<slug>/. Removes the runtime
  dependency on docs.oracle.com when authoring specs and feeds the
  pattern-lookup scorer.
- 110+ cached .drawio / .svg / .png references for offline reuse,
  plus the OCI Toolkit v24.2 import (kb/diagram/assets/oci-toolkit-drawio).

Documentation:
- docs/skill/output-formats.md — new "Standard diagram-generation
  procedure (MANDATORY)" + geometry rules + the new validator entry.
- SKILL.md option 2 — references the mandatory procedure.
- README.md — describes the spec validator, archcenter_pattern_lookup
  and description fetcher, and updates the KB-health table.

Tooling that backs the procedure (cumulative across recent sessions):
tools/archcenter_case_runner.py, archcenter_batch_driver.py,
archcenter_zip_downloader.py, drawio_visual_validator.py,
drawio_fidelity_eval.py, harvest_drawio_icon.py, import_oci_library.py,
oci_pptx_diagram_gen.py, oci_pptx_render.py, refresh_pptx_icon_index.py.

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

Makefile

@@ -1,6 +1,6 @@
 # OCI Deal Accelerator — Build Automation
 
-.PHONY: help install test validate example diagram deck full clean lint codex-package update-icons freshness freshness-refresh sync-skill sku-discover
+.PHONY: help install test validate example diagram deck full clean lint codex-package update-icons freshness freshness-refresh sync-skill sku-discover pptx-icons-refresh archcenter-benchmark-20
 
 # Use venv if present, otherwise find best available python3
 ifneq (,$(wildcard .venv/bin/python))
@@ -72,6 +72,17 @@ update-icons: ## Re-extract OCI icons after updating OCI Library.xml
 	$(PYTHON) tools/oci_icon_extractor.py
 	@echo "Updated kb/diagram/oci-icons.json from OCI Library.xml"
 
+pptx-icons-refresh: ## Refresh bundled OCI_Icons.pptx asset + manifest/index for native PPTX diagrams
+	$(PYTHON) tools/refresh_pptx_icon_index.py
+	@echo "Updated kb/diagram/oci-pptx-icons-manifest.yaml and oci-pptx-icons-index.json"
+
+archcenter-benchmark-20: ## Run 20-case Oracle Architecture Center native benchmark
+	$(PYTHON) tools/oci_archcenter_batch.py \
+		--limit 20 \
+		--threshold 0.82 \
+		--fidelity-threshold 0.90 \
+		--output-root examples/eval-2026-04-25-archcenter-native-20-v8
+
 clean: ## Remove generated output files
 	rm -f examples/sample-output/*.drawio
 	rm -f examples/sample-output/*.pptx