Clean up code comments and add algorithm citations

[tamirelazar]

Summary

Full sweep of every comment in src/ (54 files, +432/−856):

• Wrong/stale docs fixed — highlights: FrameTimer doc described the pre-flicker-fix architecture; frame_buffer claimed double-buffering that doesn't exist; max_brightness docs conflated the internal white-point divisor with the user-facing gain; dither::max_value doc was off by the actual semantics; local_variance returns a standard deviation; path_continuity is a flood-fill region-size proxy, not path tracing; nonexistent open_exclusive reference removed
• Noise deleted — narration comments restating the next line
• Verbose-but-true tightened — # Arguments blocks restating signatures → one prose sentence with the units/semantics that matter
• Citations injected (verified against sources): Jones 2010 (doi:10.1162/artl.2010.16.2.16202) in simulation; Miranda, Adamatzky & Jones 2011 (doi:10.1016/S1672-6529(11)60016-4) in audio; Ottosson 2020 OKLab post in palette.rs/gradients.rs (incl. an honest note that the red-row M/S constants predate the 2021 matrix update); Floyd & Steinberg 1976 in error_diffusion.rs; Bayer 1973 in dither.rs

Two sanctioned user-facing string fixes (not comments): placeholder yourusername URL → real repo; --quadrant help claimed "4× vertical resolution" (it's 2×2 subpixels per cell).

Verification

• Whole-branch diff check: only comment lines changed (plus the two string fixes above)
• cargo fmt --check, cargo clippy -- -D warnings (default + all-features)
• cargo test --lib 752 passed, --all-features 764, doctests 19, visual regression 46 — goldens untouched

Known issues found but out of scope (comment-only PR)

• --help renders constant paths instead of values for ~25 flags (stringify! misuse), e.g. [default: population::DEFAULT_POPULATION]
• --pause-style help lists 8 of 12 accepted styles; clap default ("minimal") disagrees with Args::default() (Vignette)
• --decay help says 0.0-1.0; validated range is 0.5-0.9999
• png.rs timestamp "uniqueness" reads subsec_nanos() of a fresh Instant (~0)