Preserve profanity scanner check fast path

[alyldas]

Summary

• Keep the profanity scanner check path allocation-aware for empty hinted input.
• Add package-local ProfanityScanHints aligned with shared text hints while keeping every hint optional.
• Return early from package-owned scanner.check() when textLength: 0 is provided.
• Preserve external fallback filter behavior for hinted empty input.
• Add regression coverage and benchmark evidence for clean, Cyrillic, obfuscation, and late-match paths.

Validation

• npm ci with a temporary npm cache
• npm run check with a temporary npm cache
• npm run benchmark:profanity with a temporary npm cache

Benchmark Evidence

Baseline origin/main:

• createProfanityFilter(): 8.0078 avg ms
• check short clean: 0.0274 avg ms
• check cyrillic clean: 0.0616 avg ms
• check long clean: 4.3929 avg ms
• check short match: 0.0037 avg ms
• check loose match: 0.0222 avg ms
• check long late match: 0.2657 avg ms
• scanner check short clean: 0.0245 avg ms
• scanner check short match: 0.0029 avg ms
• scanner scan short match: 0.0326 avg ms
• analyze short match: 0.0325 avg ms
• censor short match: 0.0330 avg ms
• check minSeverity high: 0.0030 avg ms

This branch:

• createProfanityFilter(): 8.2580 avg ms
• check short clean: 0.0261 avg ms
• check cyrillic clean: 0.0590 avg ms
• check long clean: 4.4114 avg ms
• check short match: 0.0037 avg ms
• check loose match: 0.0217 avg ms
• check long late match: 0.2603 avg ms
• scanner check short clean: 0.0243 avg ms
• scanner check hinted empty: 0.0000 avg ms
• scanner check short match: 0.0029 avg ms
• scanner scan short match: 0.0344 avg ms
• analyze short match: 0.0393 avg ms
• censor short match: 0.0343 avg ms
• check minSeverity high: 0.0032 avg ms

The runtime change adds a hinted empty-input guard for package-owned scanner checks; scanner matching behavior and dictionary contents are unchanged.

Compatibility Notes

• Public filter APIs are unchanged.
• ProfanityScanInput.hints remains optional, and existing textLength / hasNonAscii callers remain compatible.
• No dictionary entries were added or changed.

Closes #143

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fix: preserve profanity scanner check fast path
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