ci: avoid duplicate release-note failure issues

[yoen-velt]

Summary

• Mark failures as already notified when the release-note runner comments on a PR or creates its own issue.
• Make the workflow-level fallback skip duplicate issue creation when that marker exists.

Context

Run https://github.com/velt-js/docs/actions/runs/28146876179 correctly commented on PR #255 after reaching Claude, but the workflow fallback also opened a duplicate issue saying no PR was produced.

Tests

• bash -n scripts/release-notes/run-release-note-pipeline.sh
• bash scripts/release-notes/test-routing.sh && bash scripts/release-notes/test-detector.sh && bash scripts/release-notes/test-url-parser.sh && bash scripts/release-notes/test-resolver.sh && bash scripts/release-notes/test-internal-trim.sh && bash scripts/release-notes/test-slack-payload.sh
• ruby -e 'require "yaml"; YAML.load_file(".github/workflows/release-note-to-docs-pr.yml"); puts "workflow yaml ok"'

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Project	Status	Preview	Updated (UTC)
velt	🔴 Failed	–	Jun 25, 2026, 4:39 AM