Add workflow to update jsonschema_for_docs.json after each release

`bundle/internal/schema/since_version.go` reads `git tag --list 'v*'` to
compute `x-since-version` annotations. The committed file therefore goes
stale by one release as soon as the next tag is pushed: fields shipped
in that tag don't get stamped until the schema is regenerated against a
tag list that includes the new tag.

The new workflow runs on every `v*` tag push (and via workflow_dispatch),
regenerates the file from `main`, asserts that nothing other than
`bundle/schema/jsonschema_for_docs.json` changed, and pushes the update
directly to `main`.

Co-authored-by: Isaac

Author: shreyas-goenka

.github/workflows/update-schema-docs.yml

@@ -0,0 +1,103 @@
+name: update-schema-docs
+
+# Regenerate bundle/schema/jsonschema_for_docs.json after every release.
+#
+# bundle/internal/schema/since_version.go computes `x-since-version` annotations
+# from the list of `v*` git tags that exist when the schema is generated. The
+# committed file is therefore stale by one release as soon as the next tag is
+# pushed: fields shipped in that tag don't get stamped until the file is
+# regenerated against a tag list that includes it.
+#
+# This workflow runs on every `v*` tag push, regenerates the file from `main`,
+# and pushes the updated file directly to `main`.
+
+on:
+  push:
+    tags:
+      - "v*"
+
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: "Release tag this run is updating annotations for (e.g. v0.299.0). Used in the commit message only."
+        required: false
+
+permissions:
+  contents: write
+
+jobs:
+  update-schema-docs:
+    runs-on:
+      group: databricks-protected-runner-group-large
+      labels: linux-ubuntu-latest-large
+
+    steps:
+      - name: Checkout main
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          # The commit lands on main, not the tagged commit, so check main out
+          # directly. fetch-depth: 0 + fetch-tags: true ensure since_version.go
+          # can resolve `git show <tag>:bundle/schema/jsonschema.json` for every
+          # historical release.
+          ref: main
+          fetch-depth: 0
+          fetch-tags: true
+
+      - name: Setup Go
+        uses: actions/setup-go@4a3601121dd01d1626a1e23e37211e3254c1c06c # v6.4.0
+        with:
+          go-version-file: go.mod
+          cache-dependency-path: |
+            go.sum
+            bundle/internal/schema/*.*
+
+      - name: Determine release tag
+        id: tag
+        env:
+          GITHUB_REF: ${{ github.ref }}
+          INPUT_TAG: ${{ inputs.tag }}
+        run: |
+          if [ "${{ github.event_name }}" = "push" ]; then
+            tag="${GITHUB_REF#refs/tags/}"
+          else
+            tag="${INPUT_TAG:-manual}"
+          fi
+          echo "tag=$tag" >> "$GITHUB_OUTPUT"
+
+      - name: Regenerate jsonschema_for_docs.json
+        run: go tool -modfile=tools/task/go.mod task --force generate-schema-docs
+
+      - name: Show diff
+        run: git diff -- bundle/schema/jsonschema_for_docs.json
+
+      # Fail loudly if regeneration touches anything other than the docs schema.
+      # Anything else (annotations.yml, untracked files, ...) is a bug in the
+      # generator, not something we want to silently push to main.
+      - name: Assert only jsonschema_for_docs.json changed
+        id: check
+        run: |
+          changed=$(git status --porcelain)
+          if [ -z "$changed" ]; then
+            echo "No changes; skipping commit."
+            echo "skip=true" >> "$GITHUB_OUTPUT"
+            exit 0
+          fi
+          expected=" M bundle/schema/jsonschema_for_docs.json"
+          if [ "$changed" != "$expected" ]; then
+            echo "Expected only bundle/schema/jsonschema_for_docs.json to be modified."
+            echo "Actual git status --porcelain:"
+            echo "$changed"
+            exit 1
+          fi
+          echo "skip=false" >> "$GITHUB_OUTPUT"
+
+      - name: Commit and push to main
+        if: steps.check.outputs.skip != 'true'
+        env:
+          TAG: ${{ steps.tag.outputs.tag }}
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+          git add bundle/schema/jsonschema_for_docs.json
+          git commit -m "Update jsonschema_for_docs.json since-versions for ${TAG}"
+          git push origin HEAD:main