feat(ui): F8-12 — map polish (zoom invariance, labels, selection, soft radius) (#55)

* Honest pixel-space sizing for `pointRadiusPx` / `strokeWidthPx`: the
  renderer divides by the current camera scale on every
  `viewport.zoomed` so thin lines / small markers stay the same on-screen
  size at any zoom.
* Known-size planets switch to `pointRadiusWorld`, softened against the
  reference scale by `PLANET_SIZE_ZOOM_ALPHA = 0.33`; unidentified
  planets pin to a 3-px disc.
* New planet label layer renders a two-line `name / #N` legend under
  each planet (`#N` only for unidentified or when the new `planetNames`
  toggle is off). Selection now paints an inverse-fill frame around the
  selected planet's label plus an outline on the disc; the old
  selection-ring primitive is retired.
* Bombing markers swap the separate CirclePrim for a planet-outline
  overlay (damaged / wiped colour); the report deep-link moves to a
  "view bombing report" link in the planet inspector.
* Docs + tests follow: `renderer.md` reflects the new sizing contract +
  label / outline layers, vitest covers the sizing math, label
  formatting, and the new toggle, and the map-toggles e2e adds a
  persistence case for `planetNames`.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ui/frontend/src/lib/active-view/map-toggles.svelte

@@ -177,6 +177,15 @@ bottom-tabs bar.
 					/>
 					<span>{i18n.t("game.map.toggles.unreachable_planets")}</span>
 				</label>
+				<label>
+					<input
+						type="checkbox"
+						data-testid="map-toggles-planet-names"
+						checked={store.mapToggles.planetNames}
+						onchange={(e) => setFlag("planetNames", e)}
+					/>
+					<span>{i18n.t("game.map.toggles.planet_names")}</span>
+				</label>
 			</fieldset>
 			<fieldset>
 				<legend>{i18n.t("game.map.toggles.section.view")}</legend>