✨[Feat] Sprint 5 WebP Container Parser and Cleaner

[maruson08]

Summary

• adds bounded RIFF/WebP parsing with declared-container boundaries, chunk padding, maxChunks, and conservative trailing-data handling
• distinguishes VP8, VP8L, VP8X, ALPH, ANIM, ANMF, EXIF, XMP, ICCP, and unknown chunks without decoding payloads
• integrates WebP EXIF/XMP/ICCP container inspection
• adds deterministic WebP Privacy Clean with one output allocation
• removes complete EXIF/XMP chunks and their padding while preserving ICCP, image/animation chunks, unknown chunks, order, retained padding, and trailing bytes
• repairs little-endian RIFF size and only the ICC/EXIF/XMP VP8X feature bits
• adds WebP verification for observable EXIF/XMP/ICC presence
• rejects unsafe RIFF/chunk boundaries and invalid/duplicate VP8X before output
• keeps WebP EXIF at container-level detection because Sprint 5 does not guess a TIFF prefix or offset base

Test efficiency

• one small WebP builder
• one canonical cleaner fixture covers multiple metadata chunks, odd padding, VP8X repair, RIFF repair, animation/image preservation, trailing bytes, determinism, idempotency, input preservation, and verification
• table-driven malformed parser and cleaner cases
• removes two obsolete WebP unsupported/format-only placeholders
• 19 test files, 185 tests, 983 ms

Validation

• format: pass
• lint: pass
• typecheck: pass
• tests: pass
• build: pass
• package dry run: 41,801 bytes packed / 198,994 bytes unpacked
• npm audit: 0 vulnerabilities
• runtime dependencies: 0
• development dependencies: 8

PNG remains format detection only. JPEG behavior and tests remain unchanged.