Support multi-value CASE labels

[associate-1]

Difficulty: Easy — Extend case label parsing to accept comma-separated values; small AST and codegen changes.

Summary

Occam CASE statements can have multiple comma-separated values on a single label. Currently only single-value labels are parsed.

Occam syntax

CASE ch
  '*n', '*c'
    SKIP
  ELSE
    out ! ch

Proposed Go mapping

switch ch {
case '\n', '\r':
    // SKIP
default:
    out <- ch
}

Affected files

• test_bell.occ (lines 39, 77)

Work required

1. Parser: After parsing the first case value, check for comma and parse additional values
2. AST: Change CaseOption.Value from single expression to a list
3. Codegen: Emit comma-separated values in Go case clause

Part of #43.