fix: keep character classes within path portions

[lprnmns]

Problem

makeRe() could generate a character-class regexp that matched a path separator even though minimatch() correctly treats / as a path boundary. For example, makeRe('[^a]').test('/') returned true while minimatch('/', '[^a]') returned false; the same mismatch occurred after a wildcard and with a POSIX class.

Fix

Parsed character classes now reject / at each class position. The AST start check accounts for the zero-width guard so existing dotfile and traversal protections remain unchanged.

Tests

• npm test -- --disable-coverage -t0 test/make-re-path-separator.js - passed, 15/15
• npm test -- -c -t0 - passed, 6,251/6,251
• ./node_modules/.bin/oxlint src test - passed
• ./node_modules/.bin/prettier --check src test - passed
• git diff HEAD^ HEAD --check - passed

Compatibility

This narrows only the makeRe() false-positive path. It aligns generated regular expressions with existing per-path-portion minimatch() behavior; regex source snapshots change accordingly. No package API, dependency, or version change was made.

Related issue

Independent current-branch reproduction; no issue is linked. The final collision check found open PRs for other current minimatch defects, but none for this character-class/path-separator mismatch.