ui/phase-19: read-only ship-group inspector + sheet + tab dispatch

Closes Phase 19's UI surface. The inspector dispatches on the
selection variant: local / other groups render class, count, the
four tech levels, mass, cargo (type + amount when loaded),
location (planet name on-orbit, from/to/distance in hyperspace),
and — for local groups only — fleet membership + state. Incoming
groups surface origin / destination / distance / speed and the
inline ETA = ceil(distance / speed); zero speed collapses to the
designer's existing "—" placeholder. Unidentified groups render
just the (x, y) coordinates and the no-data hint, mirroring the
unidentified planet treatment.

Layout / inspector-tab plumbing:
  - inspector-tab.svelte derives selectedShipGroup against the
    rendered report and mounts <ShipGroup /> when the planet
    branch doesn't match. Stale refs (an index that no longer
    resolves after a turn refresh) collapse cleanly to the empty
    state.
  - +layout.svelte mounts <ShipGroupSheet /> alongside the
    existing planet sheet on mobile; both share the
    `effectiveTool === "map"` guard and clear-on-close.

i18n: en + ru both grow ~30 keys under
`game.inspector.ship_group.*`. Adding a key to one without the
other is a TS error (TranslationKey is `keyof typeof en`), so the
Russian mirror stays mandatory.

Tests:
  - inspector-ship-group.test.ts exercises every variant —
    on-planet local, in-hyperspace local, cargo-loaded local,
    foreign, incoming with ETA, incoming with zero speed,
    unidentified, plus the missing-planet `#NN` fallback.
  - tests/e2e/inspector-ship-group.spec.ts is a smoke spec that
    drives the DEV-only synthetic-report loader from /lobby
    through navigation to /games/synthetic-XXX/map.

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

ui/frontend/src/lib/i18n/locales/en.ts

@@ -245,6 +245,36 @@ const en = {
 	"game.designer.ship_class.preview.range": "range at full load (ly/turn)",
 	"game.designer.ship_class.preview.cargo_capacity": "cargo capacity per ship",
 	"game.designer.ship_class.preview.unavailable": "—",
+
+	"game.inspector.ship_group.kind.local": "your group",
+	"game.inspector.ship_group.kind.other": "other race group",
+	"game.inspector.ship_group.kind.incoming": "incoming group",
+	"game.inspector.ship_group.kind.unidentified": "unidentified group",
+	"game.inspector.ship_group.field.class": "class",
+	"game.inspector.ship_group.field.count": "ships",
+	"game.inspector.ship_group.field.drive": "drive",
+	"game.inspector.ship_group.field.weapons": "weapons",
+	"game.inspector.ship_group.field.shields": "shields",
+	"game.inspector.ship_group.field.cargo_tech": "cargo",
+	"game.inspector.ship_group.field.mass": "mass",
+	"game.inspector.ship_group.field.cargo_load": "cargo aboard",
+	"game.inspector.ship_group.field.location": "location",
+	"game.inspector.ship_group.field.from": "from",
+	"game.inspector.ship_group.field.to": "to",
+	"game.inspector.ship_group.field.distance": "distance remaining",
+	"game.inspector.ship_group.field.speed": "speed (ly/turn)",
+	"game.inspector.ship_group.field.eta": "ETA (turns)",
+	"game.inspector.ship_group.field.fleet": "fleet",
+	"game.inspector.ship_group.field.state": "state",
+	"game.inspector.ship_group.field.coordinates": "coordinates",
+	"game.inspector.ship_group.cargo.col": "colonists",
+	"game.inspector.ship_group.cargo.cap": "industry",
+	"game.inspector.ship_group.cargo.mat": "materials",
+	"game.inspector.ship_group.cargo.emp": "empty",
+	"game.inspector.ship_group.cargo.none": "none",
+	"game.inspector.ship_group.location.in_hyperspace": "in hyperspace",
+	"game.inspector.ship_group.fleet.none": "—",
+	"game.inspector.ship_group.unidentified_no_data": "no data — only the radar blip is known",
 } as const;
 
 export default en;