feat: add evaluation tables and data to test skills against updates

[ryzizub]

Description

Add evaluation tables and reference data so this plugin's skills can be tested against Claude Code updates. Today there is no structured way to verify a skill still behaves correctly after a Claude Code change. Define eval cases (inputs and expected outcomes) per skill so regressions are caught automatically rather than discovered in use.

Requirements

• Define an eval data format (input scenario, expected behavior/output, pass criteria) reusable across skills.
• Store eval tables/data co-located with each skill or under a shared evals/ directory.
• Seed eval cases for the core skills (bloc, testing, navigation, layered-architecture, create-project).
• Provide a runner that executes the evals and reports pass/fail.
• Document how to add a new eval case when adding or changing a skill.

Additional Context

Consumed by the weekly changelog-check bot: when a skill is flagged as potentially impacted, its eval table is the gate for confirming it still works. See #103.