[jussielo-amd]

Summary

Phase 6f-7 of the main.rs modularization (epic ROCMAI-27). Mechanical relocation, no behavior change: moves GPU/device-policy parsing and VRAM usage warning logic out of apps/rocm/src/main.rs into a new apps/rocm/src/gpu_policy.rs.

• parse_device_policy/parse_gpu_selection/parse_gpu_indices_arg, select_gpu_indices_under_launch_lock, validate_pinned_gpu_index, effective_gpu_count, auto_select_gpu_indices/select_auto_gpu_index, gpu_vram_usage and its platform-gated gpu_vram_usage_sysfs variants (moved intact, cfg-gates unchanged — no platform-support change), read_drm_vram_usage/read_sysfs_u64/drm_device_is_amd, parse_gpu_vram_usage, gpu_low_memory_warning/vram_capacity_is_meaningful/serve_gpu_low_memory_warning, busy_gpu_indices, detect_gpu_count, plus struct GpuVramUsage and AUTO_FREE_VRAM_FRACTION, interleaved but part of the same cluster.
• This cluster was documented as "staying in main.rs" by two earlier PRs in this same stack (ROCMAI-213: extract engine plugin binary resolution and IPC envelope into engine_ipc.rs #749's engine_ipc.rs, and serve_cmd.rs's pre-existing doc comment) — both corrected in this PR along with their imports, since those items are part of this ticket.
• Real external callers beyond main.rs fixed: engine_ipc.rs, serve_cmd.rs.
• An unrelated breakage from the move: advised_commands.rs's file-path allowlist for a CPU-fallback error string had to be updated to point at the new file.
• dispatch()'s Command::EngineServeHttp arm calls parse_gpu_indices_arg directly — body confirmed byte-identical (independently re-verified by SHA-256), only the import changed.
• 33 tests partitioned into the new module's own test block, including two shared test fixtures (vram(), host_gpu()) duplicated into main.rs's test module where a test that stays behind also needs them — documented inline. Total workspace test count unchanged.
• docs/architecture.md updated with this module's entry.

Test plan

• cargo build --workspace
• cargo build --workspace --all-targets --features e2e-test-hooks
• cargo clippy --workspace --all-targets -- -D warnings
• cargo fmt --all -- --check
• cargo xtask check-crate-edges
• cargo test --workspace --no-fail-fast — 4322 passed, 0 failed, 17 ignored (independently re-run, matches baseline exactly; two unrelated pre-existing timing flakes observed and confirmed to pass in isolation — therock::tests::wait_with_output_bounded_waits_unbounded_when_no_timeout_is_given and cli_progress::tests::animated_spinner_keeps_ticking_without_progress_calls, neither in a file this PR touches)
• cargo xtask manifest --check
• python scripts/smoke_local.py --profile debug --skip-build
• dispatch() call sites confirmed byte-identical (SHA-256 of the function body)
• Windows-target clippy — x86_64-pc-windows-gnu is not installed in this environment; skipped and flagged rather than silently omitted. Platform-gated code (gpu_vram_usage_sysfs's two cfg variants) moved with its cfg-gates textually unchanged, not reauthored.

Depends on #749 (ROCMAI-213) — fourth PR in the ROCMAI-86 (Phase 6f) stack.
Part of Jira ROCMAI-214 / epic ROCMAI-27.

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[Copilot]

🟡 Changes recommended

Unconditional filesystem and path imports become unused on Windows non-test targets, causing warnings-as-errors checks to fail.

1 open issue

• Gate fs and Path imports for Windows builds · New

What changed in this PR

Continues the main.rs modularization by moving GPU policy parsing, selection, and VRAM warnings into a dedicated module, with no intended behavior change.

Changes:

• Relocates GPU helpers and 33 tests into gpu_policy.rs.
• Updates caller imports and the command-message allowlist.
• Documents the new module and corrects comments about helper ownership.

Verification used the supplied diffs; the repository snapshot was unavailable, so builds and tests were not run.

File	Description
docs/​architecture.md	Documents GPU module responsibilities and callers.
apps/​rocm/​src/​serve_cmd.rs	Updates GPU imports and ownership comments.
apps/​rocm/​src/​main.rs	Removes relocated helpers and tests; imports the new module.
apps/​rocm/​src/​gpu_policy.rs	Houses GPU parsing, selection, telemetry, warnings, and tests.
apps/​rocm/​src/​engine_ipc.rs	Imports device-policy parsing from its new location.
apps/​rocm/​src/​advised_commands.rs	Updates the error-message allowlist path.

_{Review effort: Balanced}