fix(compact): size the window to the strip instead of a tuned constant

compactH was 158px, "tuned so the compact entry strip fits in a single row".
A constant tuned against a layout stops being true the moment the layout
changes, and this one outlived a strip that had since shrunk — leaving about
70px of empty window under the fields.

The frontend now measures what it rendered and asks for that height, watched by
a ResizeObserver so a strip that wraps at a narrow width is followed too. The
topbar is added as its declared h-8 rather than measured, since it is fixed.

Bounded in the backend: a measurement of zero — a layout not yet painted —
must not collapse the window, and the call is ignored unless compact is on so
nothing can shrink the normal window. Rounded to whole pixels so a sub-pixel
reflow cannot start a resize loop.

changelog.json

@@ -7,14 +7,16 @@
       "DX Cluster: a spot lifetime can be set — 5, 10, 15 minutes or your own value — after which spots leave the list and the band maps.",
       "Call lookup: QRZ.com now fills Name with the first name only, and optionally with the operator nickname instead.",
       "Entry form: a narrower left column, State beside the locator, and a new line with County, CQ, ITU and DXCC.",
-      "Station Control: the short and long path headings are repeated under the compass, at a readable size and clickable."
+      "Station Control: the short and long path headings are repeated under the compass, at a readable size and clickable.",
+      "Compact mode: the window now fits the entry strip instead of leaving a band of empty space below it."
     ],
     "fr": [
       "Cluster : « Masquer les contactés » ne masque plus un spot qui est un nouveau préfixe, comté, carré ou parc dans une contrée déjà faite.",
       "Cluster DX : on peut fixer une durée de vie des spots — 5, 10, 15 minutes ou une valeur libre — au-delà de laquelle ils quittent la liste et les band maps.",
       "Recherche d indicatif : QRZ.com remplit désormais Nom avec le seul prénom, et au choix avec le surnom de l opérateur.",
       "Saisie : colonne de gauche plus étroite, État à côté du locator, et une nouvelle ligne Comté, CQ, ITU et DXCC.",
-      "Contrôle station : les azimuts court et long chemin sont repris sous la boussole, lisibles et cliquables."
+      "Contrôle station : les azimuts court et long chemin sont repris sous la boussole, lisibles et cliquables.",
+      "Mode compact : la fenêtre épouse la bande de saisie au lieu de laisser une bande vide en dessous."
     ]
   },
   {