Fix: Remove App Slug detection

[HungKNguyen]

Turns out the /app or /installation both uses JWT authentication rather than installation token. As such we cannot detect the app slug from inside the workflow, but delegate to the parent workflow. Added documentation for this use case

[github-actions]

📋 PR Summary:
This PR removes automatic bot identity detection via GitHub API calls in favor of a new app-slug input parameter. The change simplifies the action by delegating app slug discovery to the calling workflow, since the /app and /installation endpoints require JWT authentication not available from installation tokens. Documentation was added for the new GitHub App setup pattern.

2 files reviewed

File	Changes
README.md	Added documentation for GitHub App setup with app-slug parameter
action.yml	Removed bot-identity detection, added app-slug input, updated trigger detection

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Found 3 correctness issues. Please address the high-severity issues before merging.

[HungKNguyen]

@github-actions please review again

Re-reviewing: state changed from CHANGES_REQUESTED to APPROVED

[github-actions]

📋 PR Summary:
This PR removes the automatic bot identity detection that queried GitHub's /user and /app API endpoints, replacing it with an explicit app-slug input parameter. The change delegates app slug detection to the parent workflow (using actions/create-github-app-token output) since both /app and /installation endpoints require JWT authentication which isn't available from within the action.

2 files reviewed

File	Changes
README.md	Added GitHub App setup documentation and app-slug parameter docs
action.yml	Added app-slug input, removed bot-identity detection step, updated trigger detection and reviewer request to use new input

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No issues found. Changes look good.

[HungKNguyen]

Test comment, shouldn't trigger an AI review