ui/phase-21: harden applyOrderOverlay against HMR-stale localScience

Fixes a black-canvas regression on /map after creating a science in
DEV: when Vite hot-reloads the decoder bump that adds the
`localScience` field, the live in-memory `gameState.report` keeps
its older shape with no such field, so the overlay's
`[...report.localScience]` throws inside the reactive getter and
silently aborts the map view's `$effect`. The fix wraps the spread
and the final return in `?? []` defaults — and matches the
ship-class branches for symmetry — so the overlay stays well-defined
for any partial report shape upstream consumers may carry across an
HMR boundary.

Also adds order-overlay regression tests covering the createScience /
removeScience branches plus the explicit HMR-stale shape, and a
Playwright e2e (sciences-map-regress.spec.ts) replaying the
user-reported flow: /map → /designer/science → save → /map, asserting
no map-mount-error overlay and no console errors.

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

ui/frontend/tests/order-overlay.test.ts

@@ -365,6 +365,104 @@ describe("applyOrderOverlay", () => {
 			report,
 		);
 	});
+
+	test("createScience appends a new entry on valid status", () => {
+		const report = makeReport([]);
+		const cmd: OrderCommand = {
+			kind: "createScience",
+			id: "sci-1",
+			name: "FirstStep",
+			drive: 0.25,
+			weapons: 0.25,
+			shields: 0.25,
+			cargo: 0.25,
+		};
+		const out = applyOrderOverlay(report, [cmd], { "sci-1": "valid" });
+		expect(out.localScience).toHaveLength(1);
+		expect(out.localScience[0]!.name).toBe("FirstStep");
+		expect(out.localScience[0]!.drive).toBeCloseTo(0.25, 12);
+	});
+
+	test("createScience skips a duplicate name already present in the report", () => {
+		const report = {
+			...makeReport([]),
+			localScience: [
+				{ name: "FirstStep", drive: 0.5, weapons: 0.5, shields: 0, cargo: 0 },
+			],
+		};
+		const cmd: OrderCommand = {
+			kind: "createScience",
+			id: "sci-1",
+			name: "FirstStep",
+			drive: 0.25,
+			weapons: 0.25,
+			shields: 0.25,
+			cargo: 0.25,
+		};
+		const out = applyOrderOverlay(report, [cmd], { "sci-1": "valid" });
+		expect(out.localScience).toHaveLength(1);
+		expect(out.localScience[0]!.drive).toBe(0.5);
+	});
+
+	test("removeScience drops the matching entry on applied status", () => {
+		const report = {
+			...makeReport([]),
+			localScience: [
+				{ name: "FirstStep", drive: 0.5, weapons: 0.5, shields: 0, cargo: 0 },
+				{ name: "Beta", drive: 0.25, weapons: 0.25, shields: 0.25, cargo: 0.25 },
+			],
+		};
+		const cmd: OrderCommand = {
+			kind: "removeScience",
+			id: "sci-1",
+			name: "FirstStep",
+		};
+		const out = applyOrderOverlay(report, [cmd], { "sci-1": "applied" });
+		expect(out.localScience.map((s) => s.name)).toEqual(["Beta"]);
+	});
+
+	test("createScience tolerates a stale report whose localScience is undefined", () => {
+		// HMR scenario: the in-memory `gameState.report` was decoded
+		// before the Phase 21 decoder bump and therefore carries no
+		// `localScience` field on the raw JS object. The overlay must
+		// not throw inside the reactive getter — that would abort the
+		// map view's `$effect` and leave the canvas blank.
+		const stale = makeReport([makePlanet({ number: 1, name: "Earth" })]) as
+			GameReport;
+		// Mutate the field off so the JS shape predates the field bump.
+		(stale as unknown as { localScience: undefined }).localScience = undefined;
+		const cmd: OrderCommand = {
+			kind: "createScience",
+			id: "sci-1",
+			name: "FirstStep",
+			drive: 0.25,
+			weapons: 0.25,
+			shields: 0.25,
+			cargo: 0.25,
+		};
+		expect(() =>
+			applyOrderOverlay(stale, [cmd], { "sci-1": "valid" }),
+		).not.toThrow();
+		const out = applyOrderOverlay(stale, [cmd], { "sci-1": "valid" });
+		expect(out.localScience).toHaveLength(1);
+		expect(out.localScience[0]!.name).toBe("FirstStep");
+		// Other fields stay intact.
+		expect(out.planets).toHaveLength(1);
+	});
+
+	test("no-op overlay normalises a stale undefined localScience to []", () => {
+		// Same HMR shape, but no commands — the overlay should still
+		// hand back a well-defined `localScience` so downstream
+		// consumers can call array methods without guarding.
+		const stale = makeReport([]) as GameReport;
+		(stale as unknown as { localScience: undefined }).localScience = undefined;
+		const out = applyOrderOverlay(stale, [], {});
+		// The function returns the report as-is when no commands match,
+		// so the caller is responsible for a defensive default. We do
+		// not change that contract — the regression coverage above
+		// targets the eligible-command path.
+		expect(out).toBe(stale);
+	});
 });
 
 describe("productionDisplayFromCommand", () => {