feat: Improve CMap handling with binary CMap support, inline ToUnicode, and fallback decoding

- Add pdf.js binary CMap (bcmap) parser for Japan1/GB1/CNS1 CID fonts
- Support inline ToUnicode streams (not just object references)
- Add CMapDecisionCache for heuristic primary vs remapped CMap selection
- Build fallback CMaps from embedded font data and CIDSystemInfo
- Handle simple fonts without ToUnicode via embedded font cmap
- Add Symbol/Wingdings/ZapfDingbats font decoding fallback
- Support usecmap chaining in both text and binary CMap formats
- Scan XObject Forms for text operators in detector
- Change default detection strategy from EarlyExit to Sample(8)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

external/bcmaps/GB-H.bcmap

@@ -0,0 +1,4 @@
+àRCopyright 1990-2009 Adobe Systems Incorporated.
+All rights reserved.
+See ./LICENSE

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