ci: fix the clang-format hook failing to install

[adriencaccia]

cpp-linter-hooks installs clang-format with pip at hook runtime. v1.4.0 only
requires pip>=20.3, which now fails to lay the wheel down:

pip failed to install clang-format 22.1.2
PermissionError: [Errno 13] Permission denied: .../site-packages/clang_format/data/bin/clang-format

Lint only stayed green while the prek cache survived — every cache miss rebuilt
the hook environment and went red, which is what happened on main today.
v1.6.0 requires pip>=26.1 for exactly this reason.

v1.6.0 also resolves the clang-format version from PyPI at run time instead of a
static list, so it is pinned to the 22.1.2 the sources are already formatted
with. Without the pin lint would jump to whatever PyPI publishes next (23.1.1
today) and reformat the eBPF C sources.

Verified against a fresh prek cache
(PREK_HOME=<empty dir> prek run clang-format --all-files): the hook installs,
reports clang-format version 22.1.2 and leaves the C sources untouched.

Refs COD-3543 — that issue tracks the memtrack/runner patch releases, which this
only unblocks.

[codspeed]

Merging this PR will not alter performance

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

✅ 17 untouched benchmarks

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_{Comparing fix-clang-format-hook-install (41f6539) with main (f198706)}

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge; no concrete behavioral, security, or repository-rule issue was identified.

Summary

This PR repairs cold-cache clang-format hook installation by upgrading cpp-linter-hooks and pins the formatter version to preserve stable formatting.

• Upgrades cpp-linter-hooks from v1.4.0 to v1.6.0.
• Pins clang-format to 22.1.2 while retaining the existing style and in-place formatting arguments.
• Keeps the hook scoped to the existing memtrack eBPF C sources.

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