fix: honor skipped Claude skills in validation

[KiDDarn]

What changed

• make skill:check honor the Claude host's configured skipSkills list during template coverage
• report intentionally skipped Claude-only outputs explicitly
• fail if a skipped output unexpectedly exists
• add a regression test for the claude/SKILL.md case

Why

The Claude generator intentionally skips the outside-voice claude skill, but the validator still required claude/SKILL.md to exist. That made skill:check report a missing generated file even when generation behaved correctly.

Impact

skill:check no longer produces a false failure for intentionally omitted Claude skills, while retaining protection against stale or unexpected generated outputs.

Validation

• bun test test/skill-check.test.ts (pass)
• npm test (exit 0)
• git diff --check (pass)
• gstack redaction scan over added lines: 0 findings

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