Merge pull request #692: feat(header): opt-in GPU and CPU clock readings after CPU and MEM

Conflict in config/test-suites.ts resolved by keeping both sides: #689's
header-divider and #692's header-host-sensors browser tests are both
listed in BROWSER_TEST_GLOBS.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/architecture-invariants.md

@@ -1031,7 +1031,7 @@ With `classic` nothing is left behind: no headings, no breaks, no inline order,
 
 ### Header stats styles
 
-**Header stats styles** (`headerStatsStyle`, per-device, desktop only, default `compact`; Discussion #426 option G): how the WS readout, CPU, MEM and the plan-usage windows are drawn. `tiles` gives each its own label-over-value tile with a bar along the bottom edge; `compact` is two pills, WS / CPU / MEM and the plan windows, with a ring beside every value (stat rings accent, red past 80%; plan rings green, yellow or red); `classic` is the bars and `5H · 7D` chip as before. `data-header-stats` on `<html>` (pre-paint, then `applyHeaderStatsStyle()` from `applyHeaderVisibilitySettings()`) drives every rule; narrower than 768px and in a solo window it resolves to `classic`, because the stats are hidden there anyway and the moves below would otherwise reach the phone header.
+**Header stats styles** (`headerStatsStyle`, per-device, desktop only, default `compact`; Discussion #426 option G): how the WS readout, CPU, MEM and the plan-usage windows are drawn. `tiles` gives each its own label-over-value tile with a bar along the bottom edge; `compact` is two pills, WS / CPU / MEM and the plan windows, with a ring beside every value (stat rings accent, red past 80%; plan rings green, yellow or red); `classic` is the bars and `5H · 7D` chip as before. `data-header-stats` on `<html>` (pre-paint, then `applyHeaderStatsStyle()` from `applyHeaderVisibilitySettings()`) drives every rule; narrower than 768px and in a solo window it resolves to `classic`, because the stats are hidden there anyway and the moves below would otherwise reach the phone header. The opt-in host readings after MEM (GPU, VRAM, GPU MHz, CPU MHz: `.stat-item` elements that start `hidden` and are shown by `_updateHostSensors` in panels-ui.js) rely on `html[data-header-stats] .header-system-stats .stat-item[hidden]` in styles.css outranking the Tiles style's own `display` on `.stat-item`; keep that selector's specificity above any style rule that sets `display` on a stat item, or the hidden placeholders (`--%`) reappear.
 
 ⚠️ The clustered styles need the three elements contiguous, and the template keeps the classic order, so `applyHeaderStatsStyle()` MOVES `#connectionIndicator` into `#headerSystemStats` (first child) and `#planUsageChip` right after it, and `classic` moves them back to comment anchors it left at the template positions. Ids are unchanged, so every writer still finds them. ⚠️ The indicator joins the pill only while System Stats is shown: the pill is hidden with `display: none`, and the WS readout must not disappear with it.
 

docs/wiki/Settings-Reference.md

@@ -65,6 +65,16 @@ Manager, Attachments, File Viewer, Multi-monitor, Split, Tiles, Plan Usage, Life
 Project Insights, File Browser, Subagents, Approvals Inbox, Read My Mind, Ultracode Agents,
 Ultracode Windows, Cron.
 
+**Host readings** (opt-in, both off by default and per device): **GPU Stats** adds three items after CPU and MEM: GPU load, graphics memory and the GPU clock,
+and **CPU MHz** adds the live CPU clock. Both sets of items live inside **System Stats**, so they show only
+while that chip is on, and nothing is fetched while it is off. An item appears only when the
+host reports it, so a machine with no readable GPU shows nothing extra. Sources: `nvidia-smi` or the amdgpu
+sysfs files for the GPU; inside WSL, the Windows performance counters through `typeperf.exe`, which cover
+any vendor (an Intel GPU gives load and memory in use, but Windows publishes no clock for it, and its memory
+total is taken as half of Windows' RAM, the limit Windows applies to integrated GPUs); and
+`scaling_cur_freq`, `/proc/cpuinfo` or, inside WSL, the Windows `Processor Frequency` counter for the CPU
+clock. Nothing is read, and `nvidia-smi` and `typeperf.exe` are never run, while both are off.
+
 **Bottom bar** (below the chips): **Git status** shows a small indicator at the right of the
 bottom bar, off by default and per device. It reads `● N` uncommitted files, `↑ N` commits not
 pushed, `⚠ N` merge conflicts, `? N` repositories git could not read, or `✓` when everything is