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>

kb/diagram/assets/archcenter-refs/network-for-db-at-azure/_description.md

@@ -0,0 +1,194 @@
+# Design a multicloud network to deploy Oracle Database@Azure
+
+- Source: https://docs.oracle.com/en/solutions/network-for-db-at-azure/index.html
+- Date: 2025-04
+- Type: reference-architecture
+- Services: vcn, drg, azure, fastconnect
+- Tags: networking, multicloud, azure
+
+## Summary (catalog)
+
+Network design patterns for Database@Azure deployments. Covers VNet-to-VCN peering, hub-spoke topologies, and on-premises connectivity via ExpressRoute + FastConnect.
+
+## Architecture (fetched from source)
+
+Design a Multicloud Network to Deploy Oracle Database@Azure 
+ 
+ 
+ 
+ 
+- 
+ 
+- 
+ 
+ 
+ 
+ 
+ 
+- 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+- 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+ 
+- 
+ 
+- 
+ 
+- 
+ 
+- 
+ 
+- 
+ 
+- 
+ 
+- 
+ 
+- 
+ 
+- 
+ 
+- 
+ 
+- 
+ 
+- 
+ 
+ 
+ 
+ 
+
+ Previous 
+ Next 
+ JavaScript must be enabled to correctly display this content
+ 
+ 
+
+ 
+
+ 
+ 
+ 
+Design a Multicloud Network to
+ Deploy Oracle Database@Azure 
+
+ 
+
+ 
+
+ 
+When designing multicloud networks for Oracle Autonomous Database or Oracle Exadata Database
+ Service on Microsoft Azure, it's critical to establish a strong foundation for your network
+ topology and connectivity.
+ 
+
+ 
+This playbook will help you design a multicloud network for Oracle Database@Azure by providing guidance to:
+ 
+
+ 
+ 
+- Create Oracle Database@Azure 
+ Oracle Autonomous Database and Oracle Exadata Database
+ Service designs
+ 
+ 
+- Plan the CIDR for the client delegated subnet 
+ 
+- Create the delegated subnet 
+ 
+- Understand the DNS 
+ 
+ 
+
+ 
+ 
+Replay the Webinar
+
+ 
+
+ 
+Replay the webinar: 
+
+ 
+
+ 
+
+ 
+
+ 
+
+ 
+
+ 
+
+ 
+
+ 
+ 
+Before You Begin
+
+ 
+
+ 
+ Before you begin, please familiarize yourself with the following core Oracle
+ Database service components: 
+
+ 
+ 
+- Onboarding with Oracle
+ Database@Azure 
+ 
+- Network Setup for Oracle
+ Exadata Database Service on Exascale Infrastructure
+ Instances 
+ 
+- Plan for IP Address Space in
+ Oracle Database@Azure 
+ 
+- Learn about selecting
+ network topologies for Oracle Database@Azure 
+ 
+ 
+
+ 
+
+ 
+
+ 
+
+ 
+
+ 
+ Title and Copyright Information 
+
+ 
+
+ 
+Design a multicloud network to deploy Oracle Database@Azure
+
+ 
+G28813-01
+
+ 
+April 2025
+
+ 
+ Copyright © 2025, 
+
+Oracle and/or its affiliates.