[codex] Add progress loader cell sheet preview

[newjordan]

Summary

• Add the modular dotmax::progress loader/progress style system with 586 registered styles across 52 themes.
• Add examples/loading_bars.rs for terminal browsing and examples/loading_bar_sheet.rs for generating a single self-contained HTML cell sheet.
• Check in docs/progress_loader_sheet.html, a 586-cell animated preview page with corner labels for each animation cell.
• Add the ignored-but-manifest-declared examples/test_video_decode.rs so origin/main can parse the current manifest in a clean checkout.

Validation

• cargo run --example loading_bar_sheet -> wrote 586 styles across 52 themes to docs/progress_loader_sheet.html.
• cargo check --example loading_bar_sheet
• cargo check --example loading_bars
• cargo test all_styles_render_robustly --lib
• cargo test names_unique_per_theme --lib
• git diff --cached --check

Notes

• Built and verified from a clean worktree based on origin/main so this PR is one commit ahead of main.