perf(telemetry): reduce idle resource monitoring CPU

[danvernon]

Summary

• Reduce idle resource-monitor sampling from 1 second to 5 seconds when diagnostics are not being viewed.
• Refresh expensive memory, disk, and command details only for tracked processes, preserving live diagnostics command refreshes.
• Share desktop-bootstrap polling and settings relative-time ticking across consumers.
• Document the telemetry behavior and update focused tests.

Why

The always-on telemetry path repeatedly scanned and refreshed process data, while mounted UI consumers created duplicate timers. Those redundant periodic tasks consumed CPU while the app was idle.

Validation

• cargo fmt --check --manifest-path native/resource-monitor/Cargo.toml
• cargo test --locked --manifest-path native/resource-monitor/Cargo.toml (15 passed)
• ./node_modules/.bin/vp test run apps/server/src/resourceTelemetry/NativeTelemetryClient.test.ts (10 passed)
• Targeted web typecheck, lint, formatting, and diff checks

This PR is separate from the large-thread synchronization batching PR.

Note

Reduce idle CPU usage in resource monitoring and UI polling

• In the native resource monitor, periodic background samples now refresh CPU only for all processes, then fetch memory/disk/cmd details only for tracked PIDs; command lines are re-read only when unset. Live and on-demand samples continue to refresh everything unconditionally.
• resolveNativeSampleIntervalMs now returns a 5,000ms interval when there are no live diagnostic subscribers instead of always using 1,000ms.
• useRelativeTimeTick and useDesktopLocalBootstraps are rewritten with useSyncExternalStore so multiple consumers share a single timer/polling loop that stops when there are no subscribers.
• Behavioral Change: background telemetry sampling interval increases from 1,000ms to 5,000ms when no live subscribers are present.

^{Macroscope summarized a94c104.}

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[macroscopeapp]

Approvability

Verdict: Approved a94c104

Performance optimization that reduces CPU usage by applying consistent 5-second background polling intervals, sharing timers across React components, and limiting expensive process metadata refreshes to tracked processes only. Changes are self-contained with clear intent and appropriate test updates.

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