Live process tree: collapsed rows should include their hidden children's usage

[thepradipvc]

Problem

In Settings → Maintenance → Diagnostics → Live process tree, a collapsed row shows only its own numbers. The processes it hides drop out of the table along with their usage.

On desktop, Electron main and its four helpers (GPU, network utility, two renderers) use about 1.9 GB together. The renderer alone is around 900 MB:

Collapse Electron main and the row shows the main process by itself, around 300 MB:

Collapsing is the natural way to cut noise while looking for what's using resources, but right now it hides most of the usage.

Proposal

Do what Windows Task Manager does with process groups:

• A collapsed row shows its own usage plus all hidden descendants: CPU %, CPU time, memory, read/write per second, read/write totals.
• Expanded rows keep showing their own numbers, so nothing is counted twice.
• A muted count after the name, e.g. Electron (4), with a tooltip "Includes 4 hidden processes", so a summed row isn't mistaken for one process.

Tools are split on this. Activity Monitor's hierarchical view and htop's tree view show own usage only. Windows Task Manager sums groups, and btop has an option for it. Since this table exists to answer "what is T3 using?", summing seems like the better fit.

Scope

Client-only, in the web diagnostics table. No contract or server changes; the client already receives every process with its parent PID. About 20 lines in ResourceTelemetryDiagnostics.logic.ts, the count badge in the row component, and a unit test.

The screenshots are from a working branch: thepradipvc/t3code@fix/process-tree-server-root...feat/process-tree-collapsed-totals. I'm happy to open it as a PR if the direction sounds right.

Related:

• collapsing Electron main on desktop also hid the backend server row, because Electron launches the server. That's a separate bug, fixed in fix(web): collapsing Electron main no longer hides the backend server #32619. The summing branch sits on top of it.
• Settings > Diagnostics: the resource monitor has drifted from the rest of Settings #32328 proposes a visual redesign of this page, including the process tree layout. This proposal only changes what collapsed rows show, and should work with either layout.