Migrate installers to D&V action

[puerco]

This pull request refactors all installer GitHub Actions for Carabiner tools to use a single, centralized download-and-verify action, improving maintainability and consistency of binary verification. It also introduces new configuration options for policy, context, and signers, and adds support for the policyctl tool in the test workflow. Several tool versions are updated as well.

Key changes include:

Installer Refactoring and Verification Pipeline:

• All tool installer actions (ampel, beaker, bnd, revex, snappy, policyctl) now delegate installation and verification to the shared download-and-verify action, replacing custom platform-detection and download logic with a unified, provenance-verified approach. This ensures consistent security and reduces code duplication. [1] [2] [3] [4] [5] [6]

• The download-and-verify action now supports new inputs for specifying the verification policy, context, and signers, with sensible defaults that enhance provenance validation and flexibility for downstream workflows. [1] [2]

Workflow and Tooling Updates:

• The test workflow (test-installers.yaml) is updated to include policyctl in the matrix and adds a new job to test downloading and verifying the snappy tool, further exercising the new verification logic. [1] [2] [3]

• Tool versions are updated for beaker (to v0.1.2), revex (to v0.0.2), and snappy (to v0.2.4), ensuring the workflow tests current releases. [1] [2] [3]

Other Improvements:

• Copyright years in installer action metadata are updated.
• Descriptions in action metadata are clarified for several tools. [1] [2] [3] [4] [5]

These changes collectively improve the security, maintainability, and clarity of the installer workflows for all Carabiner CLI tools.

Closes #51
Supersedes #49

[puerco]

/lgtm