Let the launcher icon catch up with the mark v2 already drew everywhere else

TitleBar and PhoneShell have drawn >_ knocked out of a solid accent tile since
v2, and both say in a comment that the launcher icon draws the same thing so the
three cannot drift. The launcher was still v1: an outlined square in the accent.
The comments are true now.

On Android the tile is the background layer rather than a rounded rectangle in
the foreground, because the rounding a launcher applies is its mask. Drawing the
tile would put a second rounded shape inside the mask, clipped at the corners on
any device whose mask is not the one it was drawn for; leaving it to the mask
gets a squircle on one device and a circle on another for free. Windows has no
mask, so dodossh.ico still draws its own corners.

The monochrome layer keeps only the glyph. A themed icon drops the background,
which is where the tile now lives, and a layer filled to the edges to stand in
for it would tint to a featureless square.

The glyph is half the width of the safe zone, taken from the two headers rather
than invented -- both set >_ a little under half the tile across. It is also
markedly more legible small than the outline was: dark on accent at 16px is a
mark, where a sub-pixel hairline was a smudge.

src/DodoSSH.Client.Android/Resources/mipmap-anydpi-v26/ic_launcher.xml

@@ -5,12 +5,17 @@
   adaptive icons landed in 26, so there is no device this ships to that would need the
   bitmaps. Density buckets exist to pick a PNG; a vector has nothing to pick between.
 
-  The background is the same @color/dodo_window the window, status bar and navigation bar
-  use, so the mark sits on the app's own near-black rather than on a second dark that is
-  almost but not quite it.
+  The background is the accent, and that is the tile itself rather than a backdrop for one:
+  the v2 mark is >_ knocked out of a solid accent square, so the square is this layer and the
+  launcher's mask is what rounds it. See ic_launcher_foreground.xml for why the rounding is
+  left to the mask instead of drawn.
+
+  It was @color/dodo_window until the mark went from outlined to filled, which is worth
+  knowing if a home screen still shows the dark version: a launcher caches icons, and the
+  cache outlives the install that changed them.
 -->
 <adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
-  <background android:drawable="@color/dodo_window" />
+  <background android:drawable="@color/dodo_accent" />
   <foreground android:drawable="@drawable/ic_launcher_foreground" />
   <monochrome android:drawable="@drawable/ic_launcher_monochrome" />
 </adaptive-icon>