chore: add claude workflow

[sissbruecker]

Adds a GitHub actions workflow for running Claude Code in CI. This allows to tag @claude in a comment on either an issue or PR and assign it an arbitrary task ("investigate this issue", "fix this bug", "implement this", "review this PR").

• The workflow triggers for comments on either issues or PRs
• The workflow is skipped, as in it does not even start a runner, when the comment does not tag @claude or if the comment author is not a maintainer.
• Grants minimal workflow permissions. It provides id-token: write, which the github-claude-action uses to create a short-lived GitHub token through the Claude Github app installed in this repo. Claude itself then runs with the GitHub app token rather than the workflow token. The app token is revoked automatically after the workflow.
• Claude is given a restricted set of tools to use. These may not be sufficient for all tasks yet and might need tuning. Running with full permissions would require additional work to not provide an Anthropic API key to the workflow and hide the GitHub workflow token from the Claude process.
• It includes an additional system prompt to reference web-components and flow checkouts that it can use for research.
• It adds a custom prompt when tagging @claude in a reply to an inline PR comment, so that Claude can scope its work to the specific comment, rather than all of them.
• A summary step collects and prints info about the Claude session and any permission issues that it ran into when calling tools. An additional step allows storing the full session JSON as an artifact. Can be enabled with a repo variable to debug issues but is disabled by default.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud