[Backport 1.0] fix(hgraph): tune from available fp32 codes

[jac0626]

Summary

Backport #2466 to the 1.0 branch.

• Let HGraph Tune select an available lossless source from raw vectors, precise FP32 codes,
  or base FP32 codes instead of relying only on store_raw_vector.
• Require the selected codes to cover the current internal ID range.
• Rebuild precise codes whose payload was omitted by ignore_reorder serialization.
• Keep Tune state publication atomic and add source-selection, serialization, ForceRemove,
  and concurrency regression coverage.

Fixes: #2465

Validation

/opt/homebrew/opt/llvm@15/bin/clang-format --dry-run --Werror \
  src/algorithm/hgraph/hgraph.cpp tests/test_hgraph.cpp
git diff --check upstream/1.0..HEAD

source ~/.zshrc && make test CASE='[tune_codes]' COMPILE_JOBS=6
  All tests passed (8040 assertions in 1 test case)

Compatibility

• API/ABI impact: none.
• This is a clean cherry-pick of the two commits from fix(hgraph): tune from available fp32 codes #2466.

[vsag-bot]

/label S-waiting-on-review
/waiting-on reviewer
/request-review @jiaweizone
/request-review @wxyucs
/request-review @inabao
/request-review @LHT129

[vsag-bot]

Automated pull request review completed.

Review effort: medium (210 changed lines across 2 files).

No actionable inline findings were found.
Review: #2475 (review)

[gemini-code-assist]

Code Review

This pull request refactors HGraph::Tune to improve thread safety, parameter validation, and resource management during index tuning, and adds comprehensive unit tests to verify tuning behavior. The review feedback suggests performing defensive parameter validation at the beginning of the function, casting signed counts to prevent compiler warnings, and refactoring the vector decoding helper to use an RAII scope guard for exception safety and check for decoding failures.

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[vsag-bot]

Automated inline review completed.

Review effort: medium (210 changed lines across 2 files).
No actionable inline findings were found.

Reviewed commit 0007698.