feat(ui): F8-12 — owner feedback round 2 (#55)

* Bug fix: theme flip no longer leaves planets oversized. The
  camera-preserving remount now calls a new
  `RendererHandle.refreshCameraDerivedDraws` explicitly after the
  manual moveCenter/setZoom pair so the post-mount geometry tracks
  `viewport.scaled` even if pixi-viewport's `'zoomed'` listener
  races the next Ticker tick.
* Doc #3: clicks on a planet label route through the same hit-test
  path as a click on the disc. The label `Container` now has a
  pointer hit area sized to the text + frame padding; pointertap
  simulates a click at the planet centre, so selection and
  pick-mode resolution behave identically.
* Doc #4: battle X-crosses + cargo arrowhead wings grow
  sub-linearly with zoom (PLANET_SIZE_ZOOM_ALPHA). New
  `Style.softLengthAnchor` ('center' / 'start') makes the renderer
  treat the recorded endpoints as the geometry "at the reference
  scale" and rescale around the midpoint (X-cross) or the start
  endpoint (arrow wings). Arrowhead base length is halved from 6
  to 3 world units to match the owner's "in half" request.
* Doc #5: picker overlay loses the anchor ring at the source, the
  cursor line drops to a cargo-route-thin 0.6 px stroke, and the
  hover ring around the destination is replaced by a planet-style
  outline (visible disc + 1 px padding) in the `pickHighlight`
  accent — so candidate destinations read like selection in warm
  yellow.
* Doc #6: regression test pins the in-disc hit zone.
* Perf #1: camera-driven redraws are throttled onto the next
  Ticker tick. A rapid wheel / pinch burst now coalesces into at
  most one `clear() + redraw` pass per painted frame, which keeps
  the 500-planet map responsive on zoom and toggle flips.

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

ui/frontend/tests/map-hit-test.test.ts

@@ -280,6 +280,21 @@ describe("hitTest — empty results and scale", () => {
 		expect(ids(w, "torus", cam05, cursorOver(516, 500, cam05))).toBe(null);
 	});
 
+	test("F8-12 / #6 — clicks inside the disc hit, not just on its edge", () => {
+		// At scale=1 with pointRadiusBasePx=10 and scaleRef=1, the
+		// visible world radius is 10. Any cursor inside that disc must
+		// resolve to the planet — the bug owner spotted in the picker
+		// was the click being ignored once the cursor moved off the
+		// circumference toward the centre.
+		const camAtRef = camAt(500, 500, 1);
+		const w = new World(1000, 1000, [
+			point(1, 500, 500, { style: { pointRadiusBasePx: 10 } }),
+		]);
+		for (const dx of [0, 2, 5, 8, 9.5]) {
+			expect(ids(w, "torus", camAtRef, cursorOver(500 + dx, 500, camAtRef))).toBe(1);
+		}
+	});
+
 	test("pointRadiusBasePx scales softly with zoom (F8-12 / #31)", () => {
 		// world 1000×1000, viewport 200×200 → scaleRef = 0.2. At
 		// scale=0.5 the on-screen pixel size is