Step 1 of file-level refactor: prove the file->directory pattern with the
cleanest possible extraction.
- src/webrtc.rs: 913 -> 741 LOC
- New src/webrtc/html_page.rs: 170-line HTML test page as pub(super) const
- Parent module re-exports via `mod html_page; use html_page::HTML_PAGE;`
so all references in handle_signaling stay unchanged.
Verification (all green):
- cargo build / cargo build --release
- cargo test (79 lib + 3 integration = 82 pass, 1 ignored — unchanged)
- cargo clippy --all-targets -- -D warnings
- cargo fmt --check
- cargo check --bin vaapi_import_bench --bin sw_encode_bench
- Test count in webrtc.rs: 18 (unchanged from baseline)
Oracle audit note: HTML_PAGE had a single use site (handle_signaling L257-258)
and zero #[cfg(test)] references, so the extraction is provably behavior-
preserving.