fix: SC refs in multi-line headers, abbrev refs on indented lines, transitive refs, isWordPattern (#38)

[theodevelop]

Type of change

• Bug fix

What does this PR do?

Fixes four false positives discovered while testing with a real-world Flex file (gnucobol's pplex.l):

1. SC refs in multi-line block headers — <SC_A,\nSC_B,\nSC_C>{ only counted the closing SC; the others had 0 refs, triggering false flex/unused-sc and showing "0 references" in Code Lens.

2. Abbrev refs on indented rule lines — {ABBR} on lines indented inside a <SC>{ } block was not counted as an abbreviation reference (actionStart was computed before stripping {name} tokens, so the leading whitespace before {ABBR} itself was misidentified as the action opener).

3. Transitive abbreviation references — abbreviations used only inside another abbreviation's definition (e.g., ALNUM_LITERAL {ALNUM_LITERAL_Q}|{ALNUM_LITERAL_A}) were never recorded as referenced, producing false flex/unused-abbrev. The parser now scans each definition body for {name} references.

4. isWordPattern with mandatory non-class groups — patterns like [_0-9A-Z]+(\.[_0-9A-Z]+)+ were classified as "word patterns" because the heuristic only checked the beginning. Such patterns require a literal dot and cannot match simple keyword strings ("IN", "OF"), yet they triggered false flex/unreachable-rule for every keyword rule that followed. isWordPattern now requires the entire pattern to consist solely of character-class groups.

Related issue

Closes #38

How to test manually

• Open a Flex file using multi-line SC block headers (<A,\nB,\nC>{) → Code Lens must show correct reference counts for all SCs; no flex/unused-sc.
• Open a Flex file with {ABBR} inside an indented SC block → no flex/unused-abbrev.
• Declare FOO [0-9] and BAR {FOO}+, use only {BAR} in rules → no flex/unused-abbrev for FOO.
• Write [A-Z]+(\.[A-Z]+)+ before keyword rules "IN", "OF" → no flex/unreachable-rule.

Checklist

• npm run compile passes with no new errors
• Tests added or updated (207 passed, 0 failed)
• Manual test done in VS Code
• CHANGELOG.md updated
• No unintended files staged (node_modules, .env, dist...)