P6.3: correct startup measurement — ~400 ms on Fyne 2.7.4

Previous commit used PowerShell process-launch timing instead of the
History tab metric. Actual warm-run figure from the in-app "Window shown
in …" event is ~400 ms, down from ~644 ms on Fyne 2.6.3 (~37% recovery).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/PERFORMANCE.md

@@ -48,10 +48,19 @@ builds, so the comparison is fair.
 - The tray / autostart path (`--start-in-tray`) skips `w.Show()` until the user
   opens the window, so it is unaffected.
 
-### Next check
+### Finding (2026-06-23, Fyne 2.7.4)
 
-Re-measure with the same method after the planned **Fyne 2.6.3 → 2.7.x upgrade**
-(see [ROADMAP.md](ROADMAP.md) → Tray Interaction). The goal is to learn whether
-2.7's driver/threading changes recover any of the ~290 ms `w.Show()` cost or
-hold it steady. Reuse the `GOSENTRY_TIMING` instrumentation pattern above; do not
-commit the temporary timers.
+**Fyne upgraded from v2.6.3 → v2.7.4** as part of Phase 6 (P6.1). Measured
+using the same method as the 2026-06-22 baseline: the History tab "Window shown
+in …" event, which records the span from application entry to `w.Show()`
+completion.
+
+**Warm-run average: ~400 ms** (down from ~644 ms on Fyne 2.6.3).
+
+### Interpretation
+
+Fyne 2.7 recovered roughly **~240 ms** (~37%) of the `w.Show()` regression that
+arrived with the 2.6 threading model change. Fyne 2.7.0's "Massive performance
+increases on rendering" and driver/threading optimisations are the likely cause.
+The upgrade is a net win: the `fyne.Do` threading API (required since 2.6) is
+retained, and the primary startup cost is substantially reduced.

docs/PRE-RELEASE-TASKS.md

@@ -111,7 +111,7 @@ These land together because both edit `domain/job.go` and `storage/store.go`.
 ### Phase 6 — Fyne 2.7 upgrade + tray click
 - [x] P6.1 — Bump Fyne to 2.7.x; rebuild
 - [x] P6.2 — `SetSystemTrayWindow` left-click-to-show
-- [ ] P6.3 — Re-measure startup → PERFORMANCE.md
+- [x] P6.3 — Re-measure startup → PERFORMANCE.md
 
 ### Phase 7 — Roadmap follow-ups
 - [ ] P7.1 — Linux test build fix (build-tagged Windows tests)