feat(header): rings for CPU and MEM in the Compact style (#426)

Compact now draws every reading the same way, ring then label then
value: CPU and MEM get an accent ring (red past 80%, like their value)
in place of the sparklines, the plan windows keep their green, yellow
or red rings, the dot separators go, and both pills share one label and
one value style. The sparkline markup, history and CSS are removed.

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

CLAUDE.md

@@ -335,7 +335,7 @@ Frontend JS modules have `@fileoverview` with `@dependency`/`@loadorder` tags. L
 
 **Tab layouts** (`tabArrangement`, per-device, default `state`; Discussion #426): `state` (option C) splits the list into needs you / waiting / working / idle (idle is `quiet`: its heading stays as the row's anchor but draws no label; `tabStateOrder: 'urgent-last'` flips the order, needs you at the bottom): rows in the desktop header strip with left-aligned labels in a measured column (the brand sits over the strip's corner, so the rows after the first start under "Codeman"), sections in the flat rail and the sidebar, inline dividers on the tablet strip, group order with no headings on phones. `case` (option A) wraps each case's tabs in one `.tab-cluster` box and hides the `-<case>` of a generated name (`.tab-name-case`). `ledger` (option B) is a CSS-only grid on the desktop header strip. `classic` is the old strip. Pure cores: `CodemanTabTriage` and `CodemanTabClusters` (constants.js). ⚠️ `state` is the flex `order` property plus `aria-hidden` heading/break elements reconciled in place by `_syncTabTriageChrome()` after BOTH render paths, never a DOM reorder (a state change is an incremental pass). ⚠️ `case` boxes ARE a DOM grouping, so the incremental path rebuilds whenever `_tabClusterLayout().key` changes; membership follows `_mobileOverviewCaseFor()` like the home screens. ⚠️ Drag only reorders within a group or box (`_isTabDropAcrossGroups()`). ⚠️ Named groups in the vertical rail win over both groupings. ⚠️ `classic` must leave no trace (no headings, no inline order, no boxes, no name split), and the ledger must not change the markup. Tests: `test/tab-triage.test.ts`, `test/tab-clusters.test.ts`. → [architecture-invariants#tab-layouts-by-state-by-case-ledger](docs/architecture-invariants.md#tab-layouts-by-state-by-case-ledger)
 
-**Header stats styles** (`headerStatsStyle`, per-device, desktop only, default `tiles`; Discussion #426 option G): `tiles` / `compact` (pill + sparklines + plan rings) / `classic` (as before), keyed on `data-header-stats` (pre-paint + `applyHeaderStatsStyle()`), forced to `classic` below 768px and in a solo window. ⚠️ The clustered styles MOVE `#connectionIndicator` into `#headerSystemStats` and `#planUsageChip` right after it; `classic` moves them back to comment anchors. ⚠️ WS joins the pill only while System Stats is shown. ⚠️ The extra parts (sparklines, tile words, rings, meters) are always rendered and hidden by default in CSS, which is what keeps `classic` unchanged; tile words are derived beside the connection descriptor, never added to it (`test/connection-indicator.test.ts` pins its shape). ⚠️ A tile is a three-row grid (label, value, bar) with pixel line-heights and the bundled JetBrains Mono; never lay the bar over a fixed-height tile (a taller system mono put the value on top of it). The WS tile's grid lives on the inner `.connection-tile`, because JS writes the indicator's `display` inline. Tests: `test/header-stats-style.test.ts`. → [architecture-invariants#header-stats-styles](docs/architecture-invariants.md#header-stats-styles)
+**Header stats styles** (`headerStatsStyle`, per-device, desktop only, default `tiles`; Discussion #426 option G): `tiles` / `compact` (two pills, a ring beside every value) / `classic` (as before), keyed on `data-header-stats` (pre-paint + `applyHeaderStatsStyle()`), forced to `classic` below 768px and in a solo window. ⚠️ The clustered styles MOVE `#connectionIndicator` into `#headerSystemStats` and `#planUsageChip` right after it; `classic` moves them back to comment anchors. ⚠️ WS joins the pill only while System Stats is shown. ⚠️ The extra parts (stat rings, tile words, plan rings, meters) are always rendered and hidden by default in CSS, which is what keeps `classic` unchanged; tile words are derived beside the connection descriptor, never added to it (`test/connection-indicator.test.ts` pins its shape). ⚠️ A tile is a three-row grid (label, value, bar) with pixel line-heights and the bundled JetBrains Mono; never lay the bar over a fixed-height tile (a taller system mono put the value on top of it). The WS tile's grid lives on the inner `.connection-tile`, because JS writes the indicator's `display` inline. Tests: `test/header-stats-style.test.ts`. → [architecture-invariants#header-stats-styles](docs/architecture-invariants.md#header-stats-styles)
 
 **Phone overview home screen** (`mobile-overview.js`, per-device `mobileOverviewEnabled`, default ON): under 600px the "C" logo shows NEEDS YOU / CURRENT / PAST SESSIONS instead of the welcome overlay, branched in `showWelcome()`/`hideWelcome()` via width-driven `shouldUseMobileOverview()`. ⚠️ The container ships `hidden` and only this module removes it: never give `.mobile-overview` a bare `display` rule (desktop does not load `mobile.css`). ⚠️ The split Run button must carry the toolbar's own classes (`btn-toolbar btn-run mode-<backend>` / `btn-run-gear`) and mobile.css must set no `background`/`color` on it; row status must mirror the session-tab alert language. PAST rows resume through the shared `resumeHistorySession()`. Status pills carry `data-i18n-skip`. → [architecture-invariants#phone-overview-home-screen](docs/architecture-invariants.md#phone-overview-home-screen)