Version 3.7.0: PDF tooling, installer hardening, video join helper, specs fix

[kigster]

Summary

Version bump to 3.7.0 covering PDF theming/tooling improvements, a more
robust Linux installer, new is.integer.between predicate, a video.sh
utility to concatenate videos with generated title cards, updated Gemfile
dependencies (including Rails 8.1.3), and a refreshed .fonts archive.

Changes

PDF / AsciiDoc pipeline

• Consolidate PDF theming on .asciidoc-pdf-theme.yml; bin/adoc2pdf
  now references the unified theme and surfaces a friendlier completion
  panel with a pdf-reduce hint.
• Rework bin/pdf-reduce:
  • Detect Ghostscript via brew --prefix and auto-install if missing.
  • Compute a real compression ratio; skip writing the output when the
    reduction is below the configured threshold.
  • Replace the old h1 header with h2bg and green success panel.
• Refresh .asciidoctor.css, add a new .asciidoctor-pretty.css, and
  update .asciidoc-pdf-theme.yml to the Titillium-based styling.
• Regenerate README.pdf against the new theme and drop the stale
  README-NEW.pdf artifact.
• Ship an expanded .fonts.tar.gz bundle to cover the new theme.

Installer (bin/bashmatic-install)

• Pre-flight the package list (unzip git curl) and short-circuit when
  everything is already available.
• Detect root vs. non-root and drop sudo when running as root instead
  of failing on a missing sudo binary.
• Run a single apt-get update before installing, and report back a
  non-zero exit code when any package is still missing afterwards.

Shell library

• lib/is.sh: add is.integer.between MIN N MAX with distinct exit
  codes for non-integer / below-min / above-max / out-of-range inputs,
  covered by test/is_test.bats.
• lib/video.sh: add video.date-time.from.epoch and
  video.join.many.by-extension, which discover clips by extension,
  prompt for a title, generate a 2-second black title card per clip with
  ffmpeg drawtext, and concatenate everything into a single MP4.

Dependencies & tooling

• Gemfile: add pdf-reader, relax openssl pin to the latest 3.x.
• Gemfile.lock / test/fixtures/Gemfile.lock: bump Rails to 8.1.3
  and pull in compatible updates for nokogiri, rack, irb, json,
  rdoc, rake, zeitwerk, bigdecimal, minitest, and friends.
• Add biome.json, package.json, package-lock.json, and yarn.lock
  to lint .asciidoctor.css via @biomejs/biome.
• .gitignore: ignore node_modules.

Tests

• test/is_test.bats: new cases exercising is.integer.between.
• test/git_test.bats: use the canonical .git suffix on REPO_URL so
  the test survives GitHub URL normalization.

Misc

• Bump .version to 3.7.0 and update the README author line / minor
  heading levels in the install section.

Backwards compatibility

• No removals from the public shell API; all additions are new
  functions. bin/adoc2pdf output is cosmetically different but the
  invocation contract is unchanged.
• The openssl Gemfile pin is loosened; downstream consumers tracking
  the prior ~> 3.3.2 pin should re-resolve their lockfiles.

Testing

• bats test/is_test.bats (new is.integer.between cases).
• bats test/git_test.bats (adjusted REPO_URL).
• Manual verification of bin/adoc2pdf → bin/pdf-reduce pipeline
  against the regenerated README.pdf.

Notes

CI currently skips a subset of tests; see prior commit history on this
branch for context.