Fix Bazel 7.7.1 compatibility for git shallow_since and clang-tidy

[Copilot]

Bazel 7.7.1 introduced breaking changes affecting the v8 git repository fetch and clang-tidy analysis, causing "build test data" and "check format with clang-tidy" GitHub jobs to fail.

Changes

• bazel/repositories.bzl: Removed timezone offset from shallow_since parameter for v8 dependency

  • Bazel 7.7+ rejects timezone suffixes in shallow_since
  • Changed "1752074621 -0400" → "1752074621"

• bazel/external/bazel_clang_tidy.patch: Override stdlib for clang-tidy compatibility

  • System clang-tidy-18 cannot resolve hermetic LLVM's libc++ headers
  • Added --extra-arg=-stdlib=libstdc++ to use system stdlib for analysis
  • Keeps actual build using hermetic libc++ unchanged

• .bazelrc: Configure clang-tidy to use system clang-18

  • Set CC=clang-18 and CXX=clang++-18 for clang-tidy config
  • Ensures analysis uses compatible toolchain with stdlib override

The clang-tidy aspect now uses system libstdc++ for analysis while the actual build continues using hermetic LLVM's libc++, avoiding header resolution conflicts.

Original prompt

Bazel 7.7.1 is failing on github job "check format with clang-tidy" neither is "build test data" . Please fix them both

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