feat(docs): split FFmpeg diagnostics report into fluid responsive multi-page portal

- Refactor `publish-feature-html.sh` to generate 4 decoupled static pages under `docs/`:
  - `docs/index.html`: A high-fidelity, interactive developer dashboard and central landing hub.
  - `docs/feature-matrix.html`: Dedicated FFmpeg 4-8 protocol and codec evolution matrix.
  - `docs/player-compatibility.html`: Standard player compatibility traps and encoding pitfalls validation suite.
  - `docs/virtual-sources.html`: High-definition pre-compiled procedural video/audio showcases.
- Standardize GitHub-style Markdown Alerts rendering blockquote post-processors (`[!NOTE]`, `[!TIP]`, etc.) across all split diagnostic pages.

Author: debugly