feat: decode common symbolic named references

[rogerchappel]

Summary

• add table-driven regression coverage for Greek letters, mathematical symbols, and arrows
• decode the common HTML 4 Greek, mathematical operator/relation, and directional arrow named-reference sets
• document supported scope, semicolon requirements, case sensitivity, and unknown-name preservation

Commits

• 48c3732 test: cover common symbolic named references
• e8d4899 feat: decode common symbolic named references
• 7b956a3 docs: describe symbolic named-reference support

Verification

• npm run release:check
• git diff --check origin/main...HEAD
• commit author/committer audit against origin/main

[rogerchappel]

Automated merge note

Triage class: auto-merge

Summary: Expands semicolon-terminated named-reference decoding with HTML 4 Greek letters, common mathematical operators and relations, and directional arrows, with focused tests and documentation (3 files, +41/-6).

Checks run: GitHub CI test — COMPLETED/SUCCESS; worker verification recorded npm run release:check (45 tests plus syntax, build, smoke, package smoke, and release contract) and git diff --check origin/main...HEAD; final full diff, mergeability, one-review branch protection, Roger Chappel author/committer identities, and head SHA re-verified.

Rebased/CI-repaired: no.

Verified head SHA: 7b956a3.