Add workflow to notify Radius repo on contrib updates

[kachawla]

Overview

Today the radius Bicep extension published to biceptypes.azurecr.io includes core namespaces (Applications.Core, Applications.Dapr, etc.) and, with radius#11915, also includes contrib resource types (Radius.Compute, Radius.Data, Radius.Security). However, when resource type manifests change in this repo, there is no automation to notify the Radius repo so it can refresh its manifest copies and republish the extension.

This PR adds a workflow that fires a repository_dispatch event to radius-project/radius whenever resource type manifests are updated on main, triggering the Radius repo's automated sync and publish pipeline.

End-to-end flow

resource-types-contrib merges to main
  |
  +--> notify-radius.yaml (this PR) fires repository_dispatch
         |
         +--> contrib-update-resource-types.yaml (radius repo) receives dispatch
                |
                +--> Runs 'make update-resource-types' to refresh manifest copies
                +--> Opens/updates PR on bot/update-resource-types branch
                       |
                       +--> Human reviews and merges the PR
                              |
                              +--> Push to main triggers build.yaml's existing
                                   build-and-push-bicep-types job
                                     |
                                     +--> Dispatches to radius-publisher
                                     +--> Publishes radius:latest to biceptypes.azurecr.io

What this PR adds

notify-radius.yaml

Trigger: Push to main touching any YAML file, excluding .github/ and docs/. This avoids hardcoding namespace folder names (Compute/, Data/, Security/) so new top-level namespace folders are automatically covered without workflow changes.

What it does:

1. Sends a resource-types-contrib-updated dispatch event to radius-project/radius using peter-evans/repository-dispatch@v3
2. Includes the commit SHA in the payload for traceability (informational only -- the Radius workflow always fetches @latest)
3. Writes a summary to the GitHub Actions UI

What happens if a non-manifest YAML changes? The Radius workflow runs make update-resource-types, finds no diff, and exits cleanly without opening a PR. A no-op CI run (~1 minute) is the only cost.

What happens if a new namespace folder is added here but not in defaults.yaml? Only types listed in the Radius repo's deploy/manifest/defaults.yaml are included in the extension. The dispatch fires but make update-resource-types finds no changes for the unlisted namespace and no PR is opened. The new types only appear in the extension when someone adds them to defaults.yaml in the Radius repo.

Dependencies

• Radius repo: Add workflow to sync contrib resource types and publish Bicep extensions -- the receiver of the dispatch
• Required secret: GH_RAD_CI_BOT_PAT with repo scope on radius-project/radius

Changes

• .github/workflows/notify-radius.yaml: New workflow

Part of

Unified Bicep extension publishing (PR 4/4). See design doc.

[DariuszPorowski]

LGTM