Small version: update command, highlighted listings, strict quality gate

[JheisonMB]

Small version of texforge, ready for review. Squash-merge: the branch carries loop commits with spec scopes.

User-facing

• texforge update: explicit, consent-first self-update with checksum verification (always asks; refuses cargo-managed installs). update --check contract: exit 0 up to date, 1 update available, 2 check failed.
• Code listings: syntect-based syntax highlighting with a per-line frame that handles page splits; the capabilities example showcases native code blocks; listings docs.

Quality

• Strict quality gate (file size, clippy complexity lints, cargo-deny, cargo-machete) passes; large modules split, dependencies updated.
• Mutation testing on the whole crate in the cloud (8 shards, memory-capped): 1348 mutants, 1287 caught, 0 missed, 0 timeouts, 61 unviable. The previous run had 53 missed and 18 timeouts; the quality pass killed them with tests and bounded loops.
• The bounded-loop rewrites in the TeX parser (for _ in 0..src.len() caps, skip_to_inline_dollar, page_breaks_from_outline, build_spell_text) are behaviour-neutral: every capped iteration consumes at least one byte or breaks. Checked on a scratch project: check (same findings), stats, outline, fmt --check, pdf pages, pdf text, pdf check produce the same output as the build before the pass.
• Two equivalent mutants excluded in .cargo/mutants.toml, each with its proof (verified).
• release.yml grants actions: read so the release reuses the binaries built in the PR to main.

Checked locally on the installed release build: new -t general, check, stats, outline, build (3-page PDF with sections, accents, \href, \lstinline, inline math with \$), pdf pages/info/check/text; cargo fmt/clippy/988 tests and rust-quality.sh green.

Known, pre-existing, queued (not in this PR): spell warnings report the line where a multi-line text token starts and print in a non-deterministic order; config tests can write to the real ~/.texforge/config.toml; the general template never \inputs sections/body.tex, leaves {{user.name}} raw without a configured name, and loads inputenc; dead level_counters state in the PDF outline walker.

🤖 Generated with Claude Code

https://claude.ai/code/session_01JeZdT4Zae1BxeLEoKd6kEs