v0.9.3

• Added SVG cover image support for EPUB thumbnails (rasterized via resvg)
• Added IsccThumbExtractionError for recoverable thumbnail extraction failures
• Changed code_iscc() to handle thumbnail extraction failures gracefully (logs warning, continues
  without thumbnail instead of raising); genuinely corrupt or invalid source files still raise
  IsccExtractionError
• Changed code_iscc() to generate thumbnails early, before heavy content processing
• Removed EPUB cover fallback to first manifest image (only explicit cover references are used)
• Fixed EPUB3 cover-image detection for manifests with multiple space-separated property tokens
• Fixed EPUB cover extraction when archive entries store UTF-8 filename bytes without the ZIP UTF-8
  flag (CP437→UTF-8 recovery)
• Fixed EPUB cover extraction for OPF hrefs containing ../. path segments
• Fixed PNG cover thumbnail extraction failing on Photoshop-exported covers with large zTXt metadata
  chunks (raised PngImagePlugin.MAX_TEXT_CHUNK to 4 MB)
• Wrapped iscc-tika parse failures (TypeError from native bridge, e.g. TIKA-237 on EPUBs with
  deeply nested XHTML) as IsccExtractionError in text_extract and text_meta_extract
• Improved API documentation for code_iscc(), code_iscc_mt(), code_content(), and
  code_text() options
• Refactored code_iscc_mt() for improved parallelism: text extraction runs before submitting
  content/semantic futures, thumbnail generation overlaps with sum/meta computation, and result
  merging follows the same order as code_iscc()
• Removed redundant onnxruntime from sci and sct optional dependency groups (already a
  transitive dependency of iscc-sci and iscc-sct)
• Fixed CI: skip semantic code tests on macOS Python 3.12 (onnxruntime 1.26.0 has no macOS wheels
  for that version)
• Updated iscc-schema floor to >=0.8.0 (version-pinned @context/$schema URLs now resolve to
  0.8.0)