fix(ui): calculator polish — smart input steps, unified tech/MAT lock idiom, tech floor, speed-lock ceiling fix

- pkg/calc: DriveForSpeed treats restMass==0 as a valid ceiling-only
  case (every positive drive solves it), so locking the displayed
  speed of a D=1, W=A=S=C=0 ship is no longer a phantom "infeasible".
- ship-design-area: drive/weapons/shields/cargo inputs use a JS-driven
  smart step on ArrowUp/ArrowDown (0↔1 jump, otherwise ±0.1) and hide
  the native spinner so it cannot produce invalid (0, 1) values;
  armament keeps its native step 1.
- Tech and planet MAT cells follow the same lock idiom as goal-seek
  locks: open padlock (🔓) over the inherited value → click to open
  an input with a closed padlock (🔒). The padlock slot is always
  reserved, so the column width is stable.
- Tech overrides (design area and modernization target) are floored
  at the player's current tech on this turn — a lower value is
  flagged as invalid.

ui/frontend/tests/calc-model.test.ts

@@ -135,6 +135,25 @@ describe("computeCalculator goal-seek", () => {
 		expect(result.blocks.drive).toBe(10);
 	});
 
+	test("speed lock is feasible at the ceiling when rest mass is zero", () => {
+		// Regression for the D=1, W=A=S=C=0 case: every block except
+		// drive is zero, so speed equals 20*driveTech (the ceiling); the
+		// solver must accept that exact target instead of flagging it
+		// as unreachable.
+		const core = makeFakeCore();
+		const result = computeCalculator(
+			input({
+				blocks: { drive: 1, armament: 0, weapons: 0, shields: 0, cargo: 0 },
+				driveTech: 1,
+				lock: { output: "speedEmpty", value: 20 },
+			}),
+			core,
+		);
+		expect(result.lockFeasible).toBe(true);
+		expect(result.computedInput).toBe("drive");
+		expect(result.outputs?.speedEmpty).toBeCloseTo(20, 9);
+	});
+
 	test("calls the matching solver with the right context", () => {
 		const weaponsForAttack = vi.fn(() => 7);
 		const core = makeFakeCore({ weaponsForAttack });

ui/frontend/tests/calculator-tab.test.ts

@@ -278,4 +278,106 @@ describe("calculator-tab", () => {
 			"15.273",
 		);
 	});
+
+	test("tech defaults render as a number with an open-lock affordance", () => {
+		const ui = mount();
+		// Default state: no override → number + open lock, no input.
+		expect(ui.getByTestId("calculator-tech-value-drive")).toHaveTextContent(
+			"1.2",
+		);
+		expect(
+			ui.getByTestId("calculator-tech-override-drive"),
+		).toBeInTheDocument();
+		expect(ui.queryByTestId("calculator-tech-drive")).toBeNull();
+	});
+
+	test("clicking the open tech lock reveals the input + closed lock", async () => {
+		const ui = mount();
+		await fireEvent.click(ui.getByTestId("calculator-tech-override-drive"));
+		// Now an input is rendered and the lock turned closed (reset).
+		expect(ui.getByTestId("calculator-tech-drive")).toHaveValue(1.2);
+		expect(ui.getByTestId("calculator-tech-reset-drive")).toBeInTheDocument();
+		expect(ui.queryByTestId("calculator-tech-value-drive")).toBeNull();
+	});
+
+	test("flags a tech override below the player's current tech", async () => {
+		const ui = mount();
+		await fireEvent.click(ui.getByTestId("calculator-tech-override-drive"));
+		// Player drive is 1.2; setting 0.5 is below the floor.
+		await fireEvent.input(ui.getByTestId("calculator-tech-drive"), {
+			target: { value: "0.5" },
+		});
+		expect(ui.getByTestId("calculator-tech-drive")).toHaveAttribute(
+			"aria-invalid",
+			"true",
+		);
+	});
+
+	test("smart step jumps from 0 to 1 on ArrowUp for ship blocks", async () => {
+		const ui = mount();
+		const drive = ui.getByTestId("calculator-block-drive") as HTMLInputElement;
+		drive.focus();
+		await fireEvent.keyDown(drive, { key: "ArrowUp" });
+		expect(drive).toHaveValue(1);
+		await fireEvent.keyDown(drive, { key: "ArrowUp" });
+		expect(drive).toHaveValue(1.1);
+		await fireEvent.keyDown(drive, { key: "ArrowDown" });
+		expect(drive).toHaveValue(1);
+		await fireEvent.keyDown(drive, { key: "ArrowDown" });
+		expect(drive).toHaveValue(0);
+	});
+
+	test("regression: speed lock works at the ceiling with all-zero non-drive blocks", async () => {
+		const ui = mount();
+		await setBlock(ui, "drive", 1);
+		// Override drive tech to 1 so the ceiling math is plain.
+		await fireEvent.click(ui.getByTestId("calculator-tech-override-drive"));
+		await fireEvent.input(ui.getByTestId("calculator-tech-drive"), {
+			target: { value: "1" },
+		});
+		// With D=1, W=A=S=C=0 the only achievable speed is 20*driveTech=20.
+		expect(ui.getByTestId("calculator-out-speedEmpty")).toHaveTextContent("20");
+		await fireEvent.click(ui.getByTestId("calculator-lock-speedEmpty"));
+		const locked = ui.getByTestId("calculator-locked-speedEmpty");
+		expect(locked).toHaveValue(20);
+		// The lock is feasible — no infeasible title and no red error class.
+		expect(locked).not.toHaveAttribute(
+			"title",
+			expect.stringMatching(/cannot be reached/i),
+		);
+	});
+
+	test("planet MAT defaults to a value + open lock and opens an input on click", async () => {
+		const selection = new SelectionStore();
+		selection.selectPlanet(17);
+		const ui = mount({
+			report: makeReport({ planets: [LOCAL_PLANET] }),
+			selection,
+		});
+		// Initial state: the MAT shows the planet's value via the number cell
+		// and an open lock; no input until the override is activated.
+		expect(
+			ui.getByTestId("calculator-planet-mat-value"),
+		).toHaveTextContent("100");
+		expect(
+			ui.getByTestId("calculator-mat-override"),
+		).toBeInTheDocument();
+		expect(ui.queryByTestId("calculator-planet-mat")).toBeNull();
+		await fireEvent.click(ui.getByTestId("calculator-mat-override"));
+		expect(ui.getByTestId("calculator-planet-mat")).toHaveValue(100);
+		expect(ui.getByTestId("calculator-mat-reset")).toBeInTheDocument();
+	});
+
+	test("flags a modernization target below the player's current tech", async () => {
+		const ui = mount();
+		await fireEvent.click(ui.getByTestId("calculator-mode-modernization"));
+		// Player drive is 1.2; the target is seeded with the same value.
+		await fireEvent.input(ui.getByTestId("calculator-target-drive"), {
+			target: { value: "0.5" },
+		});
+		expect(ui.getByTestId("calculator-target-drive")).toHaveAttribute(
+			"aria-invalid",
+			"true",
+		);
+	});
 });

ui/frontend/tests/e2e/game-shell-inspector.spec.ts

@@ -275,6 +275,9 @@ test("calculator draws reach circles for the selected planet", async ({
 	await calc.getByTestId("calculator-block-drive").fill("10");
 	await calc.getByTestId("calculator-block-shields").fill("5");
 	await calc.getByTestId("calculator-block-cargo").fill("5");
+	// Tech defaults render as a number + open lock; click to reveal the
+	// input before typing an override (the F8-06 unified lock idiom).
+	await calc.getByTestId("calculator-tech-override-drive").click();
 	await calc.getByTestId("calculator-tech-drive").fill("1.2");
 
 	await expect.poll(() => countReachCircles(page)).toBeGreaterThan(0);

ui/frontend/tests/fake-core.ts

@@ -94,10 +94,13 @@ export function makeFakeCore(overrides: Partial<Core> = {}): Core {
 		weaponsForAttack: ({ targetAttack, weaponsTech }) =>
 			weaponsTech <= 0 || targetAttack < 0 ? null : targetAttack / weaponsTech,
 		driveForSpeed: ({ targetSpeed, driveTech, restMass }) => {
+			if (driveTech <= 0 || targetSpeed <= 0) return null;
 			const ceiling = 20 * driveTech;
-			if (driveTech <= 0 || targetSpeed <= 0 || targetSpeed >= ceiling) {
-				return null;
+			if (restMass <= 0) {
+				if (targetSpeed !== ceiling) return null;
+				return 1;
 			}
+			if (targetSpeed >= ceiling) return null;
 			return (targetSpeed * restMass) / (ceiling - targetSpeed);
 		},
 		shieldsForDefence: ({ targetDefence, shieldsTech, restMass }) => {