Decode common currency and math HTML references

[rogerchappel]

Summary

• add focused decoder coverage for pound, cent, yen, notin, le, and ge named references while preserving case-insensitive lookup and unknown references
• decode those common currency and mathematical references in HTML-to-text output
• add a representative passing fixture and align CLI fixture-count coverage
• document the supported references and preservation behavior

Commits

• 7cbd393 test: cover currency and math references
• 8511322 fix: decode currency and math references
• 2470b70 docs: describe currency and math references

Verification

• npm ci
• npm run release:check (41 tests; syntax check; build; CLI smoke; packed-package smoke; release contract)
• git diff --check origin/main...HEAD
• every commit author and committer verified as Roger Chappel <miscanalysis@gmail.com>

[rogerchappel]

Automated merge note

Triage class: auto-merge.

Summary: Decode common semicolon-terminated currency and mathematical HTML named references, with focused unit, fixture, CLI, documentation, and changelog coverage (9 files, +33/-4).

Checks run: GitHub CI test completed SUCCESS; PR diff re-read; branch protection re-verified (only one approving review required, no required status checks); local npm run release:check (41 tests, syntax/build/CLI/packed-package smoke/release contract) and git diff --check origin/main...HEAD recorded by the PR author.

Rebased/CI-repaired: no.

Verified head SHA: 2470b70.