refactor: delegate pptx rendering to ai-nuts/pptx2video

[LingAo Xiao (ArmandXiao)]

Summary

• Move the complete generic PPTX renderer, Author Notes protocol, animation-order handling, TTS, subtitles, timeline, and strict QA runtime to ai-nuts/pptx2video.
• Remove the duplicated generic runtime from Paper2Video while retaining paper-specific narration and visual-cue orchestration.
• Document the installation order: install the ppt-master skill, install the pptx2video skill, then install the public pptx2video CLI runtime.
• Support direct /pptx2video skill invocation and public pptx2video render CLI usage.
• Preserve the wrapped-line cue grouping and shared FFmpeg resolution needed by Paper2Video.

Repository boundary

ai-nuts/pptx2video
  skills/pptx2video/   # directly installable /pptx2video skill
  src/pptx2video/      # public cross-platform CLI and runtime

ResearchStudio-Reel/skills/paper2video
  scripts/             # paper-specific orchestration only
  references/          # install and public-CLI bridge

This PR contains no agents/, no tests/ or test files, and no in-tree pptx2video/ runtime.

Install and invoke

npx skills add hugohe3/ppt-master --skill ppt-master
npx skills add ai-nuts/pptx2video --skill pptx2video
python -m pip install \
  "pptx2video[svg] @ git+https://github.com/ai-nuts/pptx2video.git@v0.5.0"
python -m playwright install chromium
pptx2video doctor --svg

Then invoke /pptx2video in the agent host, or call pptx2video render directly.

Validation

• 129 existing standalone and Paper2Video tests passed locally; test files are intentionally not part of this PR or the external repository.
• Both skills pass quick_validate.py.
• Public npx skills add ai-nuts/pptx2video --skill pptx2video installation succeeds.
• Public pip installation from tag v0.5.0 succeeds and reports pptx2video 0.5.0.
• Wheel and source distribution builds succeed.
• git diff --check passes.

Supersedes

Supersedes #25 and #29.