[FEA] Remove precompiled header directory specifications

[lamarrr]

Description

Follow-up to #22812
Removes manual PCH cache directory specification for LTO fragment compilation.
It was already removed for the pure CUDA-only path.

Checklist

• I am familiar with the Contributing Guidelines.
• New or existing tests cover these changes.
• The documentation is up to date with these changes.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Run ID: b4e0f508-fdec-4d98-beee-0f806acbed1f

📥 Commits

Reviewing files that changed from the base of the PR and between cb88f9b and ccec3ae.

📒 Files selected for processing (3)

• cpp/src/jit/cache.cpp
• cpp/src/runtime/context.cpp
• cpp/src/runtime/context.hpp

💤 Files with no reviewable changes (3)

• cpp/src/jit/cache.cpp
• cpp/src/runtime/context.cpp
• cpp/src/runtime/context.hpp

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📝 Summary

Summary by CodeRabbit

• Changes
  • Removed support for configuring a separate directory for just-in-time compilation precompiled headers.
  • JIT compilation no longer creates or uses a dedicated PCH cache directory.
  • Existing precompiled-header controls and verbosity options remain available and unchanged.

Walkthrough

The JIT context no longer manages a PCH directory. The fragment compiler no longer passes --pch-dir to NVRTC. Existing PCH and verbosity options remain.

Changes

JIT PCH directory removal

Layer / File(s)	Summary
Remove JIT PCH context state cpp/src/runtime/context.hpp, cpp/src/runtime/context.cpp	The context configuration and accessor no longer expose a JIT PCH directory. Initialization no longer creates or constructs the directory.
Simplify NVRTC PCH options cpp/src/jit/cache.cpp	compile_fragment no longer retrieves a PCH directory or passes --pch-dir to NVRTC.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Merge Risk: ⚪ Minimal · up to ccec3

The JIT LTO compilation path no longer supplies a manual PCH directory, aligning it with the CUDA-only path. No current merge-readiness risk is identified.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The description clearly explains that the PR removes manual PCH cache directory specification for LTO fragment compilation and aligns this path with the CUDA-only path.
Title check	✅ Passed	The title clearly and concisely identifies the removal of precompiled header directory specifications, which is the main change.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[lamarrr]

/merge