feat: per-GPU health gauges on NVLink/XGMI tabs and capacity-based bar colors

[crazyguitar]

Purpose

Adds simple GPU monitoring to the GPU tabs (inspired by all-smi/nv-monitor) and makes bar colors reflect link saturation.

Test Result

Checklist

• cargo fmt --check passes
• cargo clippy -- -D warnings passes
• cargo test passes
• Tested on RDMA-capable hardware (or explained why not in the Test Plan)
• Docs/README updated if behavior or flags changed

[Copilot]

Pull request overview

This PR adds a shared per-GPU “health” metric struct and wires NVML (NVLink) + amdsmi (XGMI) readers to populate it, then renders those metrics as a gauge strip and extra detail lines in the GPU tabs. It also updates throughput bar coloring to reflect saturation against link capacity (when known), rather than absolute Gbps.

Changes:

• Introduces GpuMetrics (util/VRAM/temp/power/clock) and populates it from both NVML (NVIDIA) and amdsmi (AMD).
• Renders per-GPU health gauges in the GPU tabs and adds a utilization sparkline (fixed 0–100 scale) in detail panes.
• Colors throughput bars by % of link capacity when available, with a fallback to the prior absolute-Gbps coloring.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/xgmi.rs	Adds amdsmi FFI structs/entry points and captures per-GPU health metrics in XGMI snapshots.
src/nvlink.rs	Captures per-GPU health metrics via NVML and attaches them to NVLink snapshots.
src/gpu.rs	New shared GpuMetrics struct used by both GPU backends and the TUI.
src/tui/ui.rs	Adds gauge strip + detail rendering for GPU health; adds capacity-based color helpers and refactors bar rendering.
src/tui/app.rs	Threads metrics into TUI metadata and records utilization history for sparklines.
src/tui/theme.rs	Adds a good_dim color used in the new capacity gradient.
src/main.rs	Registers the new gpu module.

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated no new comments.

[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated no new comments.