docs(hip-kernel-provider): correct backend and runtime guidance

[tenpercent]

JIRA ID : AICK-1593

Summary

Stage 5 of 5. Reconcile backend, lowering, runtime, and troubleshooting guidance with current code, including LLVM-flavor datalayout selection, gfx-selected wave and atom facts, runtime library discovery, and the stale BUILD.md link.

Pilot stage map

• Stage 1: docs(hip-kernel-provider): refresh rocKE architecture foundations #9764 — architecture foundations
• Stage 2: docs(hip-kernel-provider): preserve address-planning design #9963 — address-planning future design
• Stage 3: docs(hip-kernel-provider): relocate gfx950 attention case study #9964 — gfx950 attention case study
• Stage 4: docs(hip-kernel-provider): relocate gfx942 attention case study #9965 — gfx942 attention case study
• Stage 5: docs(hip-kernel-provider): correct backend and runtime guidance #9966 — backend, lowering, and runtime guidance

This is a five-stage review-workflow pilot. We will stop after Stage 5 and ask maintainers whether these boundaries are reviewable before splitting any remaining audit work.

Review size

• 7 files, 291 changed lines
• Within the agreed limit: target at most 650 lines and 6 files; hard limit fewer than 800 lines and fewer than 8 files.

Test plan

• Committed-range pre-commit hooks passed.
• git diff --check passed.
• Full dsl_docs relative-link scan: 59 checked, 0 broken.
• Focused current-source validation passed: 45 CPU tests, 1 toolchain capability skip.
• Before the split, the full documentation audit ran on gfx950 in a Kreb ROCm image: verify_dsl_docs reported 49 passed and 0 failed; the README implicit-GEMM manifest verification reported bad=0.
• GPU validation was not rerun for this docs-only stage commit; it changes no runtime source.

[therock-pr-bot]

✅ All Checks Passed — Ready for Review

Check	Status	Details
🌿 Branch Name	✅ Pass	—
📝 PR Title/Description	✅ Pass	—
⛔ Forbidden Files	✅ Pass	—
🧪 Unit Test	✅ Pass	PR does not contain code files — Unit Test auto-passed
🔎 pre-commit	✅ Pass	—
🚫 Draft PR	🔜 To Be Enabled	—
🚩 Feature Flag	🔜 To Be Enabled	—
📊 Code Coverage	🔜 To Be Enabled	—
🤖 therock-pr-bot	✅ Pass	—

🎉 All checks passed! This PR is ready for review.

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[therock-pr-bot]

🎉 All checks passed! This PR is ready for review.