PR1.5: render low-confidence warnings in Markdown

[kymuco]

Summary

Closes #77.

Makes low-confidence and input-suitability warnings visible in human-readable Markdown artifacts, without changing scoring or JSON payload contracts.

Changed

• Added shared Markdown warning helpers for confidence/suitability notes.
• Rendered concise warning blocks in:
  • report.md;
  • single-take practice_plan.md;
  • top-level batch_report.md;
  • top-level batch practice_plan.md.
• Warnings explain why confidence is lower:
  • analysis confidence level;
  • input suitability status;
  • duration mismatch;
  • start-region issues;
  • limited alignment/voicing/onset evidence.
• Added action-oriented next-recording guidance:
  • record the same section as the reference;
  • trim obvious silence;
  • use a count-in / clearer first note;
  • reduce leading noise;
  • avoid stops/restarts/unrelated sections.
• Added unit coverage for one low-confidence Markdown rendering path.

Tests

Not run locally in this environment: repository execution is handled through GitHub connector only here. The patch is reporting-only and adds matching unit coverage for the new low-confidence Markdown section.