Step 2 of plan.md (Spor B B3 pipeline run). Wires the --regex/-r flag
into main(): when set, compileRegex(pattern) is used and the count is
text.match(re).length. Invalid regex exits 2 via the existing fail()
helper. JSON output now includes flags.regex so consumers can tell the
mode apart. Baseline tests remain green; -i/--ignore-case has no effect
when --regex is set (out of brief scope).
Verify covered: SC #1 (any position), SC #2 (-r short form), SC #3
(regex semantics differ), SC #4 (invalid exits 2), SC #5 (JSON regex),
SC #6 (byte-identical baseline).
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Kjell Tore Guttormsen
44d7f339f5