Updates the Claude Code GitHub Action to use the stable v1 GA release instead of the beta version.
## Changes
- Updates action version from `@beta` to `@v1`
- Migrates `allowed_tools` to `claude_args: --allowedTools`
- Migrates `custom_instructions` to `claude_args: --system-prompt`
- Retains `additional_permissions` and `assignee_trigger` (both still supported in v1)
## Behavior
The action continues to work the same way:
- Triggers on `@claude` mentions in comments, reviews, and issues
- Triggers when assigned to an issue as "claude"
- Allows Claude to run Bash commands
- Allows Claude to read CI results on PRs
- Applies custom instructions for posting concise summaries
