fix(desktop): stop the update overlay looking frozen while it works

Two ways the update overlay read as stuck even though the update was
streaming progress underneath:

- In-app (macOS/Linux) UpdatesOverlay: runStreamedUpdate forwards every
  stdout line as a progress event with percent: null, and ingestProgress
  wrote that straight through — clobbering the milestone percents (10/60)
  so the bar fell back to indeterminate on every log line. Keep the last
  percent when a line carries null.

- Staged install/update overlay: the bar is completedCount / totalCount,
  which counts only *finished* stages, so a long first stage pinned it at
  "0 of 2" / 0% until the stage ended. Count the running stage as half a
  unit so the bar advances during the stage (the per-stage spinner already
  shows which step is live).

Both are display-only; no stage/event semantics change. (The Windows
hermes-setup Tauri progress UI in apps/bootstrap-installer has the same
counter-only-on-completion logic — parity follow-up.)

apps/desktop/src/components/desktop-install-overlay.tsx

@@ -407,7 +407,11 @@ export function DesktopInstallOverlay({ enabled = true }: DesktopInstallOverlayP
 
   const totalCount = stages.length
   const failed = Boolean(state.error)
-  const progressPct = totalCount > 0 ? Math.round((completedCount / totalCount) * 100) : 0
+  // Count the running stage as half-done so the bar advances *during* a long
+  // stage instead of sitting frozen at the last completed step while its logs
+  // stream (e.g. "0 of 2" pinned at 0% for the whole first stage).
+  const progressUnits = completedCount + (!failed && currentStage ? 0.5 : 0)
+  const progressPct = totalCount > 0 ? Math.round((progressUnits / totalCount) * 100) : 0
   const currentStartedAt = currentStage ? state.stages[currentStage]?.startedAt : null
   const currentElapsed = typeof currentStartedAt === 'number' ? formatElapsed(now - currentStartedAt) : ''
 

apps/desktop/src/store/updates.ts

@@ -531,7 +531,9 @@ function ingestProgress(payload: DesktopUpdateProgress): void {
     applying: !terminal,
     stage: payload.stage,
     message: payload.message,
-    percent: payload.percent,
+    // Streamed log lines carry percent: null; keep the last milestone percent
+    // (10/60/…) instead of resetting the bar to indeterminate on every line.
+    percent: payload.percent ?? current.percent,
     error: payload.error,
     // 'manual' carries the command to run in its message field.
     command: payload.stage === 'manual' ? payload.message : current.command,