feat(desktop): reconcile live tool events, polish thread chrome, harden boot

- chat-messages: match tool rows by overlapping query/context/preview values
  so preview-first `tool.progress` rows reliably adopt later stable-id
  `tool.start` payloads instead of spawning ghost rows or mis-merging
  parallel same-name calls; preserve prior args/result across phases.
- tui_gateway: emit full args + parsed result on `tool.start` / `tool.complete`,
  drop redundant `tool.started` re-emit from `tool.progress`.
- electron/main: prefer SOURCE_REPO_ROOT before PATH `hermes` in dev so
  local backend edits actually run; split hardening helpers into
  `electron/hardening.cjs` with tests.
- thread/tool UI: one-shot enter animation keyed by stable ids, braille
  spinner for running rows, Cursor-like disclosure rows, drill-down +
  duration/count formatting via new tool-fallback-model.
- composer: extract `text-utils`, drop liquid-glass overrides.
- right-rail: split preview-pane into preview-console / preview-file.
- runtime: incremental external-store runtime + runtime-readiness gate;
  onboarding store + tests; route-resume hook test.
- regression tests for live tool reconciliation (parallel tools, id-less
  progress, preview-first rows, structured args/results).

apps/desktop/src/components/Backdrop.tsx

@@ -30,7 +30,10 @@ function binaryNoiseDataUrl(tile: number, density: number, size: number, color:
     return ''
   }
 
-  const dpr = Math.min(window.devicePixelRatio || 1, 2)
+  // Cap at 1.5x to match the design-language overlay perf work (PR #14):
+  // with `image-rendering: pixelated` there's no visible win above 1.5x, and
+  // a full retina (2x) PNG is ~78% larger to keep resident in compositor memory.
+  const dpr = Math.min(window.devicePixelRatio || 1, 1.5)
   const physTile = Math.round(tile * dpr)
   const block = Math.max(1, Math.round(size * dpr))
 
@@ -165,7 +168,7 @@ export function Backdrop() {
 
       {import.meta.env.DEV && <ThemeControls />}
 
-      {statue.enabled && (
+      {statue.enabled && gpuTier > 0 && (
         <div
           aria-hidden
           className="pointer-events-none fixed inset-0 z-2"