Add loop mode (--loop): repeat movement until user activity

Introduce a continuous "loop" setting so a triggered sweep keeps the
cursor moving until the user moves the mouse (or Ctrl+C), instead of
firing a single sweep.

- strategies.ts: add optional `loopPath` to MovementStrategy; give `line`
  and `diagonal` infinite loop generators that pick a direction once and
  ramp forever (4px/step). Their finite `path` and declared `bounds` are
  unchanged, so single-sweep behavior is identical.
- executor.ts: add ExecuteOptions { restore?, bounds?, loop? }. Omitting
  options reproduces the original single-sweep contract exactly.
- keeper.ts: in loop mode, run an infinite loopPath once (stopped only by
  interruption) or chain a finite path cycle after cycle; force `reflect`
  bounds for every pattern and suppress the between-cycle restore, so
  line/diagonal bounce edge-to-edge instead of stopping at the first edge.
- config plumbing: new boolean `loop` through config.default.json,
  config.ts, configFile.ts, cli.ts (-l/--loop), and move.ts, mirroring
  the existing `verbose` precedence.
- docs: README loop-mode section + usage/validation updates; CHANGELOG
  Unreleased entry.
- tests: loopPath generators, executor options (bounds override, loop
  selection, restore suppression), config/configFile loop plumbing, and
  keeper-level loop behavior (ramps far vs. bounded single-sweep, chained
  cycles). 79 pass.

tests/keeper.test.ts

@@ -89,3 +89,37 @@ describe("runKeeper", () => {
         expect(dev.commanded.length).toBe(0);
     });
 });
+
+describe("runKeeper — loop mode", () => {
+    const maxX = (pts: Point[]): number => pts.reduce((m, p) => Math.max(m, p.x), -Infinity);
+
+    test("loop mode ramps far from the start via the infinite loopPath", async () => {
+        // `line`'s loopPath ramps x by 4px/step from the start and never
+        // restores, reflecting off the screen edge. From x=100 it climbs well
+        // past a single finite sweep's reach before the budget stops it.
+        const dev = new LoopDevice(400, { x: 100, y: 100 });
+        await runUntilStop(quietConfig({ moveInterval: 0, pattern: "line", loop: true }), dev);
+        expect(maxX(dev.commanded)).toBeGreaterThan(1000);
+    });
+
+    test("single-sweep mode restores each sweep, so x never ramps away", async () => {
+        // Same setup without loop: `line` runs 250 one-pixel steps then snaps
+        // back to the start, so x is bounded by start + 250 no matter how many
+        // sweeps fire within the budget.
+        const dev = new LoopDevice(400, { x: 100, y: 100 });
+        await runUntilStop(quietConfig({ moveInterval: 0, pattern: "line", loop: false }), dev);
+        expect(maxX(dev.commanded)).toBeLessThanOrEqual(350);
+    });
+
+    test("loop mode chains a finite pattern across multiple cycles per trigger", async () => {
+        // `figureEight` has no loopPath, so loop mode chains its 90-step path.
+        // A single trigger keeps chaining cycles until the budget stops it,
+        // yielding far more than the 90 commands one cycle would.
+        const dev = new LoopDevice(400, { x: 800, y: 500 });
+        await runUntilStop(
+            quietConfig({ moveInterval: 0, pattern: "figureEight", loop: true }),
+            dev,
+        );
+        expect(dev.commanded.length).toBeGreaterThan(180);
+    });
+});