feat: skip Claude step gracefully when Anthropic API is unavailable

## Summary

- Add pre-flight API availability check before running
`claude-code-action`
- Skip the Claude step gracefully (warning, not failure) when the API
returns 5xx or is unreachable
- Belt-and-suspenders: `continue-on-error: true` + post-execution
re-check distinguishes service outages from legitimate errors

## Problem

When the Anthropic API is down, the Claude step fails with a hard error,
blocking the entire CI pipeline. Example: [dotCMS/core run
24461196854](https://github.com/dotCMS/core/actions/runs/24461196854)

```
API Error: 500 {"type":"error","error":{"type":"api_error","message":"Internal server error"}} · check status.claude.com
```

## Solution

Two layers of protection in `claude-executor.yml`:

**Layer 1 — Pre-flight check** (catches most outages):
- `curl` the `/v1/models` endpoint with a 15s timeout before running
Claude
- 5xx / network failures → `available=false` → skip Claude step → warn
and succeed
- Auth errors (401/403), rate limits (429) → `available=true` → proceed
so action can surface the specific error

**Layer 2 — Runtime protection** (catches mid-execution degradation):
- `continue-on-error: true` on the Claude step
- Post-execution step checks if Claude failed
- If failed AND API is now returning 500 → skip gracefully (service
issue)
- If failed AND API is now returning 200 → re-fail with "legitimate
error" message

## Test

Validated in `dotCMS/core-workflow-test#460`:
- Pre-flight check correctly passes when API is available
- `Handle Claude execution result` correctly re-fails for non-service
errors (workflow validation failure in test PR)
- The skip path is code-correct (would activate when API returns 5xx)

## Consumer repos to update after merge

- `dotCMS/core` — update `@v2.0.0` → new tag
- `dotCMS/core-workflow-test` — update `@v2.0.0` → new tag

Fixes: dotCMS/core#35328

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: sfreudenthaler

.github/workflows/claude-executor.yml

@@ -13,6 +13,7 @@
 # - Configures the anthropics/claude-code-action with configurable claude_args
 # - Handles the actual Claude AI interaction
 # - Provides a single source of truth for Claude execution configuration
+# - Gracefully skips when the Claude API is unavailable (5xx / network errors)
 #
 # USAGE: Called by orchestrator workflows with different parameters
 # for interactive vs automatic modes and different tool configurations.
@@ -66,12 +67,82 @@ jobs:
         with:
           fetch-depth: 1
 
+      # Pre-flight check: verify the Claude API is reachable before attempting execution.
+      # Treats 5xx responses and network failures as "unavailable" and skips gracefully.
+      # Auth errors (401/403) and rate limits (429) still proceed so the action can surface them.
+      - name: Check Claude API availability
+        id: api-check
+        run: |
+          echo "Checking Claude API availability..."
+          HTTP_CODE=$(curl -s -o /dev/null -w "%{http_code}" \
+            --max-time 15 \
+            --retry 2 \
+            --retry-delay 3 \
+            -H "x-api-key: ${{ secrets.ANTHROPIC_API_KEY }}" \
+            -H "anthropic-version: 2023-06-01" \
+            "https://api.anthropic.com/v1/models" 2>/dev/null) || HTTP_CODE="000"
+
+          echo "API response code: $HTTP_CODE"
+
+          case "$HTTP_CODE" in
+            200)
+              echo "available=true" >> "$GITHUB_OUTPUT"
+              echo "✅ Claude API is available"
+              ;;
+            500|503|529|000)
+              echo "available=false" >> "$GITHUB_OUTPUT"
+              echo "::warning::Claude AI service is unavailable (HTTP $HTTP_CODE). Skipping Claude Code step. Check https://status.anthropic.com"
+              ;;
+            *)
+              # For auth errors (401/403), rate limits (429), or unexpected codes:
+              # proceed and let the action report the specific error.
+              echo "available=true" >> "$GITHUB_OUTPUT"
+              echo "HTTP $HTTP_CODE received — proceeding with Claude execution"
+              ;;
+          esac
+
       - name: Run Claude Code
         id: claude
+        if: steps.api-check.outputs.available == 'true'
+        continue-on-error: true
         uses: anthropics/claude-code-action@v1
         with:
           anthropic_api_key: ${{ secrets.ANTHROPIC_API_KEY }}
           prompt: ${{ inputs.prompt }}
           claude_args: ${{ inputs.claude_args }}
           use_sticky_comment: "true"
           track_progress: "true"
+
+      # If the Claude step failed at runtime, re-check the API to determine whether
+      # the failure was caused by service degradation (skip gracefully) or a real error
+      # (fail the job so the team is alerted).
+      - name: Handle Claude execution result
+        if: steps.api-check.outputs.available == 'true' && steps.claude.outcome == 'failure'
+        run: |
+          echo "Claude Code step failed. Checking if this is due to service unavailability..."
+          HTTP_CODE=$(curl -s -o /dev/null -w "%{http_code}" \
+            --max-time 10 \
+            -H "x-api-key: ${{ secrets.ANTHROPIC_API_KEY }}" \
+            -H "anthropic-version: 2023-06-01" \
+            "https://api.anthropic.com/v1/models" 2>/dev/null) || HTTP_CODE="000"
+
+          echo "Post-execution API check: HTTP $HTTP_CODE"
+
+          case "$HTTP_CODE" in
+            200)
+              echo "::error::Claude Code step failed and the API is currently reachable — this appears to be a legitimate error. Review the logs above."
+              exit 1
+              ;;
+            *)
+              echo "::warning::Claude Code step failed due to API service degradation (HTTP $HTTP_CODE). Skipping gracefully."
+              echo "For current service status, visit: https://status.anthropic.com"
+              ;;
+          esac
+
+      - name: Claude service unavailable — step skipped
+        if: steps.api-check.outputs.available != 'true'
+        run: |
+          echo "::warning::Claude AI Orchestrator was skipped because the Claude API is currently unavailable."
+          echo "The pipeline continues normally. Claude review will run on the next PR push when the service is restored."
+          echo ""
+          echo "For current service status, visit: https://status.anthropic.com"