The two-tool architecture previously had both tools returning identical
`SystemStats` data. This refactors them to properly separate concerns:
- `get-system-info` (Model-visible): Returns static system configuration
(hostname, platform, CPU model/count, total memory) sent once via
`ontoolresult`
- `poll-system-stats` (App-only): Returns dynamic metrics (per-core CPU
timing, memory usage, uptime) polled every 2 seconds
Moves `formatBytes()` and `formatUptime()` utilities to the client since
the server now returns raw values for client-side formatting.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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