docs: reconcile the documentation with the code

An audit of every document against the source turned up drift that had
accumulated since the 1.0.2 passes. The screenshot paths README and
DEVELOPMENT still point at are deliberately left alone - the images move
again when they are retaken.

ARCHITECTURE: the jobs_view.go split is six files, not five, since
extracting jobs_view_state.go was never counted; the statistics table
lists TimedRunCount, which the AvgDurationMS formula already referenced;
the store edge of the diagram names methods that exist (LoadJobs and
LoadConfig never did); and startup says that Service.Start is called from
newMainView rather than from Run.

TESTS: three tests had no entry, the latter two being regression tests
for 1.0.2 fixes:

  TestLoadOrCreateConfigPreservesZeroRetentionLimits
  TestWriteJSONReplacesFileAtomically
  TestQuoteLeadingWindowsProgramPathPicksEarliestBoundedExtension

The deliberately-uncovered list now covers everything the profile
actually reports at 0%, so the next redundancy pass does not flag Config,
Paths, SaveJobs, or the isEvent markers as gaps. The coverage section
measures through -coverprofile and says outright that the per-package
percentages -coverpkg prints are not the total - 2.6/8.9/25.5/1.0/61.5
against a real 84.1%.

ROADMAP: the over-the-guideline table was re-measured (service.go is over
it too now, making six), with a note to re-measure rather than trust it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

assets/assets.go

@@ -17,7 +17,7 @@ import (
 // The hard constraint: Fyne's a.SetIcon and SetSystemTrayIcon each take ONE
 // image, which the OS then scales to every size it needs — titlebar (~16px),
 // taskbar/dock (~32-48px), and tray. Neither source survives that scaling:
-// downscaling the 1254px gosentry-icon-big.png to 16px is muddy, and upscaling
+// downscaling the 1254px gosentry-icon-large.png to 16px is muddy, and upscaling
 // the 16px icon to 32px is blurry. The fix is to feed each surface a
 // size-appropriate source — which differs per platform because each platform
 // exposes different icon channels.