ci: Fail fast on pre-commit violations

[gorsing]

Summary

This PR refactors the CI workflows to improve efficiency and maintainability by extracting the pre-commit checks into a reusable workflow and making the main build matrix dependent on its success.

Motivation & Benefits

1. Fail-Fast Mechanism: Currently, the heavy build matrix (Linux, macOS, Windows, FreeBSD with multiple compilers) starts immediately on every PR. If a PR fails a basic pre-commit check (e.g., changelog formatting), it wastes 20-60 minutes of CI time before failing. With this change, the main job is blocked (needs: call-precommit) until pre-commit checks pass, catching trivial errors in ~1 minute.
2. Resource Efficiency: By preventing the heavy matrix from running on PRs that will inevitably fail basic linting/formatting rules, we save GitHub Actions minutes and reduce the CI queue load for other contributors.
3. Zero Logic Change: This is purely an orchestration refactoring. The actual commands, tools, and validation rules remain exactly the same. The risk of regression is minimal.