Say what is known about a world, and how it is known

Four changes to the readout panel and the body cards, which between them were showing less than
the catalogues hold and not always distinguishing a measurement from an inference.

Picking a planet used to navigate straight to /body/:id. That tore down the system scene and the
camera with it, so comparing two planets meant flying back into the system between each. Hovering
a body now raises a card over the live view and clicking pins it; Full view still opens the route
for the full 3D inspection. Clicking empty space unpins, and leaving the system clears it.

The card and the detail page were assembling "what do we know about this world" independently,
which is the shape of bug where a planet reads 255 K in one panel and 254 K in the other. Both now
build from one shared view model.

Orbital period was absent everywhere. For a heliocentric orbit it follows exactly from the
semi-major axis, because in these units the Sun's mass is the unit of mass — Mars comes back
687.0 d against a published 686.98. It is deliberately not computed for moons, whose elements are
relative to a parent planet the catalogue has no mass for, nor for exoplanets: periodDays is
populated for none of the 6319 shipped records and hostStarMassSolar for none either, so any
figure would assume a solar-mass host and mis-state every planet around an M dwarf. Where a period
does exist it is filed under Measured or Derived according to which it is, not by its field name.

The system readout showed a flat 0.00 pc for the Sun's distance, which is arithmetically right and
reads as a bug — the distance from here to here is not a measurement, so it is suppressed. It
gains the host star's luminosity, marked as derived, and counts moons separately from planets. The
neighbourhood readout gains the one thing the star field cannot show: how many of those points can
actually be entered. Derived readouts carry a marker and a footnote saying so.

Every quantity now formats through one module whose precision follows magnitude, rather than a
fixed decimal count per call site that read as false precision at one end and lost real
information at the other: 0.0026 AU stays legible instead of rounding to 0.00, and Pluto's period
reads 248 yr rather than 90560 d.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WaySiNst4HhDXBHnMy8p5G

src/app/features/galaxy-system/starmap-hud.component.ts

@@ -5,6 +5,12 @@ import { ViewLevel } from '../../shared/state/navigation.store';
 export interface HudReadout {
   readonly label: string;
   readonly value: string;
+  /**
+   * True when the figure was computed from other measurements rather than catalogued directly.
+   * Marked in the panel and explained in its footnote, so a reasoned number is never mistaken for
+   * an observed one.
+   */
+  readonly derived?: boolean;
 }
 
 interface LadderStep {
@@ -100,14 +106,14 @@ const LADDER: readonly { level: ViewLevel; label: string }[] = [
           <dl class="mt-3 flex flex-wrap gap-x-6 gap-y-1">
             @for (readout of readouts(); track readout.label) {
               <div>
-                <dt class="text-[10px] tracking-[0.18em] text-muted uppercase">{{ readout.label }}</dt>
+                <dt class="text-[10px] tracking-[0.18em] text-muted uppercase">{{ readout.label }}@if (readout.derived) {<span class="text-accent/80" aria-hidden="true">*</span>}</dt>
                 <dd class="text-sm text-text tabular-nums">{{ readout.value }}</dd>
               </div>
             }
           </dl>
         }
-        @if (note()) {
-          <p class="mt-3 border-t border-border/50 pt-2 text-[10px] leading-relaxed tracking-[0.08em] text-muted uppercase">{{ note() }}</p>
+        @if (note() || hasDerived()) {
+          <p class="mt-3 border-t border-border/50 pt-2 text-[10px] leading-relaxed tracking-[0.08em] text-muted uppercase">@if (hasDerived()) {<span class="text-accent/80">*</span> Derived, not catalogued. }{{ note() }}</p>
         }
       </div>
 
@@ -127,6 +133,9 @@ export class StarmapHudComponent {
   readonly readouts = input<readonly HudReadout[]>([]);
   /** Standing caveat for the current view, e.g. that galactic structure is a model. */
   readonly note = input('');
+  /** Whether any readout needs the derived-value footnote. */
+  readonly hasDerived = computed(() => this.readouts().some((readout) => readout.derived));
+
   /** Camera range, pre-formatted by the scene, which is the only thing that knows the units. */
   readonly range = input('');
   readonly showReticle = input(true);