Runnable example project for installation validation

[bradjin8]

Repository: local-ci-test-system
Severity: Medium

Problem

Local CI requires four external prerequisites — Python 3.10+, Docker, act, and yq — but the eval identifies a "Prerequisite Fog" compound that makes first-run validation nearly impossible. The name "yq" is shared by at least three different tools (mikefarah/yq, kislyuk/yq, the Python pip package "yq"), and the README does not specify which one. A PyYAML fallback exists in cli/localci/utils/yq.py when yq is absent, meaning the wrong yq doesn't always fail — it silently degrades. No prerequisite verification command exists (no localci doctor equivalent). This ambiguity compounds with a six-layer configuration model — .localci.yml, image-registry.yml, GHA workflow YAML, Docker, act configuration, and the scoring algorithm's internal logic — whose interactions are not directly observable. A new user who struggles to install the right yq then cannot distinguish "installation is broken" from "configuration is wrong," because no runnable example exercises the full config → workflow → act → results path.

Acceptance Criteria

• examples/ directory with a minimal sample project
• Includes: sample workflow YAML, config file, container registry reference
• README.md in examples/ with step-by-step validation instructions
• Running the example produces clear success/failure output
• Works on Linux (primary), with notes for macOS/Windows

Implementation Notes

• The example should exercise the core path: config → workflow → act → results
• Keep it minimal: single job, single step, immediate completion
• Reference the prerequisite docs from PR Clarify yq prerequisite #35 (yq clarification)