Implement triager role for issue/patch management

[LiranCohen]

The `ForgeRepoProtocol` defines a `triager` role alongside `maintainer` and `contributor`, but no code currently uses the triager role for authorization decisions.

Expected behavior

• Triagers should be able to update issue status (open/closed) via `co-update`
• Triagers should be able to add labels/tags to issues and patches
• Triagers should NOT have push access to git repos (that's maintainer/contributor only)

Tasks

• Add triager-specific actions to `ForgeIssuesDefinition` and `ForgePatchesDefinition` (if not already present)
• Update CLI `issue` and `patch` commands to support status changes (`dwn-git issue close `)
• Verify the `PushAuthorizer` correctly excludes triagers from push access
• Add tests for triager role interactions