Strengthen feedback escalation coverage

[SilverSupplier]

Summary

• Strengthen feedback escalation tests for repeated failures and assisted success states.
• Verify stable metadata such as assist level, hintShown, assisted, and failure count without pinning full copy strings.
• Replace brittle CSV substring checks with checks against the final assist-related CSV fields.
• Add a small reason-hint fallback so empty recognition hints still produce a family-specific action hint.

Verification

• Unity EditMode tests: 28 passed
• Unity PlayMode tests: 6 passed
• node scripts/validate-doc-state.mjs
• GitHub build, test, validate-docs, and codeql checks

Notes

• This PR is scoped to regression coverage and a defensive fallback for [Child #14] feedback escalation 테스트 보강 #40.
• It does not change the larger base/overlay copy introduced in Improve overlay failure hints #59 and Improve base family failure hints #60.

Closes #40