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/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",
+		);
+	});
 });