feat(plugin-sdk): expose optional GPU and disk metrics

[alvinunreal]

Summary

• add optional aggregate GPU and system-volume usage fields to ctx.system.metrics()
• collect from bounded, host-owned probes with five-second caching and no plugin process or file access
• extend the SDK/test harness contract and document availability semantics

Validation

• focused system-metrics TypeScript compile and behavior test
• SDK typecheck

The full desktop test build is currently blocked before compilation by pnpm 11 rejecting the repository’s pre-existing unresolved openclaw and tree-sitter-bash build approvals.

[greptile-apps]

Greptile Summary

The PR extends ctx.system.metrics() with optional host-probed GPU and system-volume usage, adds five-second caching, updates SDK and harness types, and documents availability semantics.

• Adds platform-specific GPU probes and system-volume statfs collection.
• Wires extended metrics through the Electron host and public SDK contract.
• Adds focused collector tests and registers them with the desktop test runner.

Confidence Score: 4/5

The PR should not merge until multi-device GPU values satisfy the advertised aggregate contract; probe latency and missing conformance coverage are additional non-blocking issues.

The new collectors consistently select the busiest GPU or engine rather than aggregate machine utilization, so supported multi-device hosts can return materially misleading SDK data.

Files Needing Attention: apps/desktop/src/system-metrics.ts, packages/sdk/src/index.ts, packages/sdk/src/check-plugin-sdk.ts

Important Files Changed

Filename	Overview
apps/desktop/src/system-metrics.ts	Adds bounded cross-platform GPU and disk probes, but reports peak device or engine utilization as aggregate usage and can impose multi-second fallback latency.
apps/desktop/src/plugin-host-capabilities.ts	Integrates extended metrics with in-flight deduplication and five-second caching while awaiting probes before returning required metrics.
packages/sdk/src/index.ts	Extends the public metrics result with optional GPU and disk fields, but the corresponding conformance coverage was not updated.
packages/sdk/src/testing.ts	Extends the deterministic harness metrics shape consistently with the public SDK.
apps/desktop/tests/system-metrics.test.ts	Covers synthetic collector behavior on Linux and Windows but not multi-device aggregation or SDK and harness propagation.
apps/desktop/scripts/run-tests.mjs	Correctly registers the new focused behavior test in the desktop test runner.
apps/desktop/src/plugin-sdk-bridge.ts	Keeps the host capability type aligned with the newly exposed optional fields.
docs/sdk.md	Documents optional availability and the aggregate, non-identifying nature of the added metrics.

Sequence Diagram

sequenceDiagram
    participant P as Plugin
    participant B as SDK bridge
    participant C as Host metrics cache
    participant M as Platform probes
    P->>B: ctx.system.metrics()
    B->>C: capabilities.system.metrics()
    alt cache valid
        C-->>B: cached GPU/disk fields
    else cache expired
        C->>M: GPU command/sysfs probe + statfs
        M-->>C: optional aggregate fields
        C-->>B: CPU/memory + optional GPU/disk
    end
    B-->>P: OpenPetsSystemMetrics

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_{Reviews (1): Last reviewed commit: "feat(plugin-sdk): expose optional GPU an..." | Re-trigger Greptile}

[alvinunreal]

Addressed all Greptile findings in f204216:

• GPU samples are averaged rather than reported as peak values.
• Optional GPU/disk probes run in the background; CPU and memory return immediately.
• Added SDK conformance coverage for the optional metrics round trip.

Focused system-metrics test and the SDK contract test pass. Greptile re-review reports no findings.