The AssemblyStore format documentation in Documentation/project-docs/AssemblyStores.md was outdated and contained several inaccuracies compared to the actual C++ implementation. This PR updates the documentation to reflect the current format as defined in src/native/clr/include/xamarin-app.hh.

Key Changes

Store Location and Architecture

• Updated store location: Assembly Store files are now correctly documented as being placed in architecture-specific lib/ directories within APK/AAB archives, not the assemblies/ directory
• Clarified architecture handling: There exists only one Assembly Store per architecture (not separate architecture-agnostic and architecture-specific stores)
• Added ELF embedding detail: Assembly Store files are found inside ELF shared libraries

Struct Definitions

• Corrected AssemblyStoreHeader fields: Updated from outdated local_entry_count, global_entry_count, store_id to actual entry_count, index_entry_count, index_size
• Fixed struct name: Changed AssemblyStoreAssemblyDescriptor to correct AssemblyStoreEntryDescriptor
• Added missing field: Included mapping_index field in the descriptor structure

File Format Description

• Updated format layout: Now matches the C++ comment format with correct sections: [HEADER], [INDEX], [ASSEMBLY_DESCRIPTORS], [ASSEMBLY_NAMES], [ASSEMBLY DATA]
• Corrected index structure: Updated to use AssemblyStoreIndexEntry with platform-specific hash types

New Native Struct Documentation Section

• Added dedicated section: Complete documentation of the three key C++ structures
• Included proper syntax: Full struct definitions with [[gnu::packed]] attributes
• Platform-specific details: Explained xamarin::android::hash_t type variations for 32-bit vs 64-bit platforms

File References

• Updated header path: Corrected from obsolete src/monodroid/jni/xamarin-app.hh to current src/native/clr/include/xamarin-app.hh

The documentation now accurately reflects the Assembly Store format implementation and provides developers with correct information for understanding the binary file structure.

Fixes #10265.

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