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-topology-oracle-database-at-google-cloud/_description.md

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+# Learn about selecting network topologies for Oracle Database@Google Cloud
+
+- Source: https://docs.oracle.com/en/solutions/network-topology-oracle-database-at-google-cloud/index.html
+- Date: 2025-10
+- Type: reference-architecture
+- Services: vcn, drg, google-cloud
+- Tags: networking, multicloud
+
+## Summary (catalog)
+
+Network topology options for Database@Google Cloud. Covers VPC-to-VCN peering, shared VPC, and Private Service Connect patterns. Guidance on DNS resolution and IP address management.
+
+## Architecture (fetched from source)
+
+Architecture
+
+ 
+
+ 
+This architecture shows a detailed topology for
+ Oracle AI Database@Google
+ Cloud :
+ 
+
+ 
+ Description of the illustration google-detailed-arch.png 
+
+ google-detailed-arch-oracle.zip 
+
+ 
+The architecture displays application resources within a
+ VPC of a Google Cloud project, located in a single zone of a Google Cloud region. An application subnet in the VPC connects to Oracle AI Database@Google
+ Cloud using the ODB network in the OCI child site, located in the same Google Cloud region. The client subnet of the Oracle Autonomous AI Database Serverless , the Oracle Exadata Database Service on Dedicated
+ Infrastructure client subnet, and the backup subnets of Oracle Database Autonomous
+ Recovery Service are defined in the ODB network . The VCN extends into the OCI region to enable connections to other resources within
+ OCI. The OCI region hosts the following OCI services: OCI Vault , OCI Object Storage , and control plane.
+ 
+
+ 
+
+ 
+
+ 
+ 
+Considerations for
+ Networking
+
+ 
+
+ 
+When selecting a network topology, consider the following
+ requirements:
+
+ 
+ 
+- Select or create an ODB network to associate your Oracle Autonomous AI Database or Oracle Exadata Database
+ Service .
+ 
+ 
+- Carve out a non-overlapping CIDR range with the VPC subnets. 
+ 
+- Define one CIDR for the client and backup subnet to accommodate future
+ growth. 
+ 
+ 
+
+ 
+Note:
+ Oracle Autonomous AI Database is automatically configured for local backups in the OCI region. Both the backup and
+ restore processes are initiated through Oracle Database Autonomous
+ Recovery Service .
+ 
+
+ 
+
+ 
+
+ 
+
+ 
+
+ 
+
+ 
+ Title and Copyright Information 
+
+ 
+
+ 
+Learn about selecting network topologies for Oracle AI Database@Google Cloud
+
+ 
+G13167-06
+
+ 
+April 2026
+
+ 
+ Copyright © 2024,2026, 
+
+Oracle and/or its affiliates.

kb/diagram/assets/archcenter-refs/network-topology-oracle-database-at-google-cloud/google-detailed-arch-oracle/readme.txt

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+The diagram you downloaded is available in these formats:
+- DRAWIO
+- SVG
+
+You can customize them for your organization using the associated tools:
+- For DRAWIO format, use draw.io for Confluence, online at diagrams.net, or the desktop app. Go to diagrams.net for more information.
+- For SVG format, use an SVG editor such as Inkscape or Sketsa SVG Editor, which are free and available for Windows, macOS, Linux.