fix: CMake arch auto-detection SIGILL, typos, and improved error messages

[redbasecap-buiss]

Summary

This PR fixes several bugs and code quality issues:

🐛 Bug Fix: SIGILL on x86_64 CPUs without AVX-512 (Fixes #128, Fixes #92)

Root cause: _detect_x86_best() in cmake/option.cmake iterated from the highest microarchitecture (graniterapids) downward and picked the first one the compiler accepted. Since compilers accept all -march= flags regardless of the host CPU, building on a machine with a modern compiler but an AVX2-only CPU would emit AVX-512BW instructions, causing SIGILL at runtime.

Fix: Replace the flawed probe loop with -march=native, which targets the actual build machine's instruction set.

📝 Typo Fixes

• check_need_adjuct_ctx → check_need_adjust_ctx — misspelled method name across 6 files in both dense and sparse HNSW implementations
• wiht → with in index_reducer.h, index.cc, mixed_streamer_reducer.*
• spase → sparse in hnsw_builder_entity.h, hnsw_sparse_builder_entity.h
• seperate → separate in vector_column_indexer.h
• Orignal → Original in cosine_converter.cc error message
• Full-width ！ → ! in cpu_features.h/.cc Doxygen comments
• Extra space in README.md align=" center" → align="center"

💬 Improved Error Message (Related to #78)

When using cosine metric with INT8 data without a quantizer, the error was a bare "Unsupported data type: " with no actionable detail. Now explains that cosine without quantizer only supports FP32/FP16 and suggests using QuantizerType::kInt8.

Changes

File(s)	Change
cmake/option.cmake	Fix -march= auto-detection to use -march=native
6 HNSW files	Rename adjuct → adjust
8 source files	Fix various typos
src/core/interface/index.cc	Improve cosine+INT8 error message
src/ailego/internal/cpu_features.*	Fix full-width comment character
README.md	Fix HTML attribute spacing

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