ui/phase-16: pick any planet in reach + stronger pick-mode dim

The cargo-route picker filtered out unidentified planets, so an
early-game player who had spotted but not surveyed a destination
could not configure a route to it — the engine has no such
restriction (`game/internal/controller/route.go.PlanetRouteSet`
only checks ownership of the origin and `util.ShortDistance(...) <=
FligthDistance`). Drop the unidentified guard and document the
contract in `cargo-routes-ux.md` plus a comment over `reachableSet()`.

Pick-mode dim now drops both alpha and tint on out-of-reach
planets so bright shapes (`STYLE_LOCAL` is `0x6dd2ff`) collapse
into a single muted gray. The single-channel `dimAlpha=0.3` was too
gentle against the dark theme — the user reported the dim wasn't
visible. Tighten to `dimAlpha=0.35 + dimTint=0x303841`; restore
both on tear-down.

Also threads through the user's `pkg/calc/race.go.FligthDistance`
addition: `calc-bridge.md` records the new Go-side reference (the
engine's `Race.FlightDistance()` already wraps it), and the picker
comment points at the canonical formula location.

Tests:
- `inspector-planet-cargo-routes.test.ts` adds two cases — a
  reach-spans-every-kind case (own + foreign + uninhabited +
  unidentified all picked when in range) and a successful pick to
  an unidentified destination.
- All 356 vitest cases + chromium-desktop / webkit-desktop e2e
  cargo-routes pass.

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

ui/frontend/src/map/pick-mode.ts

@@ -151,10 +151,20 @@ export function computePickOverlay(
  * PICK_OVERLAY_STYLE captures the colours / widths the renderer
  * applies to each spec channel. Exported so tests and future themes
  * can read the same values.
+ *
+ * `dimAlpha` and `dimTint` are applied together to non-reachable
+ * primitives during a pick session: the alpha drops their
+ * brightness, and the tint multiplies their fill colour toward dark
+ * gray so the colour identity (planet kind) collapses into a
+ * single muted shade. The combination has to read as "obviously
+ * disabled" against the dark theme — bright planets such as
+ * `STYLE_LOCAL` (`0x6dd2ff`) survive a 0.3 alpha alone too
+ * comfortably, so the tint pulls them down too.
  */
 export const PICK_OVERLAY_STYLE = {
 	anchor: { color: 0xffe082, alpha: 0.9, width: 2 },
 	line: { color: 0xffe082, alpha: 0.5, width: 1 },
 	hover: { color: 0xffe082, alpha: 1, width: 2 },
-	dimAlpha: 0.3,
+	dimAlpha: 0.35,
+	dimTint: 0x303841,
 } as const;