[databricks-zerobus-ingest] Region tables omit GCP entirely (and are stale for AWS/Azure) — agents conclude "Zerobus is not available on GCP"

Review skills/databricks-zerobus-ingest/references/1-setup-and-authentication.md, references/5-operations-and-limits.md, and SKILL.md, then compare their region guidance with the three linked Databricks availability pages. Update the affected guidance so GCP and current AWS/Azure availability are represented, and ensure the endpoint and troubleshooting references point to authoritative information. Done means all three files no longer imply Zerobus is unavailable on GCP.

Problem or opportunity

The databricks-zerobus-ingest skill ships static "supported regions" tables that list only AWS and Azure:

• skills/databricks-zerobus-ingest/references/5-operations-and-limits.md — "Regional Availability": ### AWS Supported Regions (9 regions) and ### Azure Supported Regions (11 regions); no GCP section.
• skills/databricks-zerobus-ingest/references/1-setup-and-authentication.md — "Supported Regions" (same two clouds) and the endpoint-format table, which has rows for AWS and Azure only.

Current Databricks docs say otherwise:

• GCP: Zerobus Ingest is documented for Databricks on Google Cloud (https://docs.databricks.com/gcp/en/ingestion/zerobus-overview, endpoint format <workspace-id>.zerobus.<region>.gcp.databricks.com at https://docs.databricks.com/gcp/en/ingestion/zerobus-ingest) and the Ingestion availability table lists 9 GCP regions (asia-south1, asia-southeast1, europe-west2, europe-west3, us-central1, us-east1, us-east4, us-west1, us-west4): https://docs.databricks.com/gcp/en/resources/feature-region-support#ingestion
• AWS: 14 regions today (e.g. eu-west-2, ap-south-1, sa-east-1, us-west-1, ap-northeast-2 are missing from the skill): https://docs.databricks.com/aws/en/resources/feature-region-support#ingestion
• Azure: ~24 regions today (e.g. uksouth, germanywestcentral, francecentral, japaneast, brazilsouth are missing from the skill): https://learn.microsoft.com/en-us/azure/databricks/resources/feature-region-support#ingestion-availability

Impact: an agent that follows the skill (which its troubleshooting table points to: "Region not supported → check supported regions in references/5-operations-and-limits.md") reads the absence of a GCP section as "not supported on GCP". In our case this went into a decision-grade evaluation as "Zerobus is not available on GCP; use a file-based path for GCP partners" and was only caught by a human checking the docs. Observed with plugin version 0.2.14; main (v0.2.16) still has the same tables.

Proposed change

1. Replace the hard-coded region tables in both reference files with a pointer to the per-cloud "Ingestion availability" tables (the three URLs above), or keep the tables but add a GCP section and a "last verified" date plus the same pointer.
2. Add the GCP row to the endpoint-format table in 1-setup-and-authentication.md.
3. Make the SKILL.md troubleshooting entry ("Region not supported") point to the docs page rather than the static table.

Affected skill or area

skills/databricks-zerobus-ingest (references/1-setup-and-authentication.md, references/5-operations-and-limits.md, SKILL.md troubleshooting table).

Additional context

Region lists were checked against the three docs pages on 2026-09-11. No customer data or identifiers involved.