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>

config/pptx-icon-library.yaml

@@ -0,0 +1,117 @@
+asset:
+  bundled_path: kb/diagram/assets/OCI_Icons.pptx
+  manifest_path: kb/diagram/oci-pptx-icons-manifest.yaml
+  index_path: kb/diagram/oci-pptx-icons-index.json
+  env_var: OCI_ICONS_PPTX_PATH
+  search_globs:
+    - /mnt/c/Users/*/Downloads/OCI_Icons*.pptx
+    - ~/Downloads/OCI_Icons*.pptx
+    - kb/diagram/assets/OCI_Icons*.pptx
+
+refresh:
+  sync_discovered_asset_into_bundle: true
+  choose_newest_discovered_match: true
+
+instruction_index:
+  noise_contains:
+    - "copyright"
+    - "oracle and/or its affiliates"
+  noise_exact:
+    - "tip"
+
+semantic_markers:
+  connectors_logical:
+    title_contains: "Connectors"
+    all_text:
+      - "Open Arrowhead style"
+      - "Bark color"
+      - "relationships between icons and grouping boxes"
+  connector_labels:
+    all_text:
+      - "connector labels"
+      - "Place connector labels on the horizontal portions"
+  grouping:
+    title_contains: "Grouping"
+    all_text:
+      - "OCI Region"
+      - "Availability Domain"
+      - "Compartment"
+  landscape_blank_template:
+    all_text:
+      - "Landscape Blank Template"
+      - "Location Canvas"
+      - "OCI Region"
+  portrait_blank_template:
+    all_text:
+      - "Portrait Blank Template"
+      - "OCI Region"
+  landscape_sample_db_dr:
+    all_text:
+      - "Landscape Sample"
+      - "Primary"
+      - "Standby"
+      - "Database"
+      - "VCN"
+  database_icons:
+    title_contains: "Database"
+    any_text:
+      - "ADB-D"
+      - "ATP-D"
+      - "ADW-D"
+      - "Data Guard"
+  migration_icons:
+    title_contains: "Migration"
+    any_text:
+      - "Database Migration"
+      - "Oracle Cloud Migration Advisor"
+
+extracted_shapes:
+  grouping_labels:
+    - "OCI Region"
+    - "Availability Domain"
+    - "Fault Domain"
+    - "Tier"
+    - "Tenancy"
+    - "Compartment"
+    - "VCN"
+    - "Subnet"
+  database_icon_labels:
+    - "Database"
+    - "Oracle Autonomous Database"
+    - "ADW-D"
+    - "ATP-D"
+    - "ADB-D"
+    - "Oracle Exadata Database Service"
+    - "Data Safe"
+    - "NoSQL Database"
+    - "Database Management"
+    - "Data Guard"
+    - "Data Guard Recovery"
+
+design_tokens:
+  palette:
+    bark: "312D2A"
+    bark_soft: "66615C"
+    gray_divider: "9E9892"
+    gray_tick: "C8C5C1"
+    bg_warm: "FBF6F0"
+    white: "FFFFFF"
+    oracle_red: "C74634"
+    oracle_red_soft: "AE562C"
+    oracle_blue: "3F7CC4"
+    oracle_green: "00875A"
+    oracle_amber: "E8A92F"
+    tl_green: "EAF2DE"
+    tl_yellow: "FBF1C7"
+    tl_amber: "F8D9A8"
+    tl_red: "F6CAC4"
+  typography:
+    primary_font: "Oracle Sans"
+  connector_style:
+    line_width_emu: 12700
+    line_width_soft_emu: 9525
+    color: "312D2A"
+    arrowhead:
+      type: "triangle"
+      width: "sm"
+      length: "sm"