Add reusable workflows for common CI/CD patterns

[JacobPEvans]

Parent

Part of #1

Task

Create reusable workflows in .github/workflows/ that other repos can call.

Proposed Workflows

1. standard-python-ci.yml - Python linting, testing, type checking
2. standard-nix-ci.yml - Nix flake check, build, formatting
3. standard-terraform-ci.yml - Terraform fmt, validate, plan
4. label-sync.yml - Sync labels from .github to calling repo

Usage Pattern

# In other repos
jobs:
  ci:
    uses: JacobPEvans/.github/.github/workflows/standard-python-ci.yml@main
    with:
      python-version: '3.11'

Acceptance Criteria

• At least 2 reusable workflows created
• Documentation in README for how to call them
• Example caller workflow provided

[JacobPEvans]

Completed. The reusable workflow set has grown well beyond the original four proposed (standard-python-ci, standard-nix-ci, standard-terraform-ci, label-sync). Current .github/workflows/_*.yml inventory:

• _ci-gate.yml — conditional required-check + queue watchdog
• _release-please.yml + _release-please-auto-merge.yml — versioning and changelog
• _python-security.yml + _osv-scan.yml — vulnerability scanning
• _markdown-lint.yml — docs linting
• _nix-build.yml + _nix-validate.yml — Nix CI
• _file-size.yml — tiered file-size enforcement
• _cribl-pack-validate.yml — Cribl pack validation
• _retrigger-pr-checks.yml — bot PR re-trigger helper
• _gh-aw-pin-refresh.yml — gh-aw SHA pin refresh
• _copilot-setup-steps.yml — Copilot environment setup

Implementing PR(s): #70, #71, #91, #98, #128, #132, #207, #247, #269.

Closing as completed.