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/strategies.test.ts

@@ -36,6 +36,16 @@ function mulberry32(seed: number): () => number {
     };
 }
 
+/** Pull the first `n` points from a (possibly infinite) point iterable. */
+function take(iter: Iterable<Point>, n: number): Point[] {
+    const out: Point[] = [];
+    for (const p of iter) {
+        out.push(p);
+        if (out.length >= n) break;
+    }
+    return out;
+}
+
 function ctxOf(overrides: {
     start?: Point;
     width?: number;
@@ -67,6 +77,14 @@ describe("line", () => {
         expect(pts[1]!.x).toBe(88);
         expect(pts.at(-1)!.x).toBe(90 - 250);
     });
+
+    test("loopPath ramps x forever at a fixed step, y held constant", () => {
+        const start = { x: 500, y: 300 };
+        const pts = take(line.loopPath!(ctxOf({ start })), 5);
+        // Monotonic +4 per step (LINE_LOOP_STEP), no vertical drift.
+        expect(pts.map((p) => p.x)).toEqual([504, 508, 512, 516, 520]);
+        expect(pts.every((p) => p.y === 300)).toBe(true);
+    });
 });
 
 describe("diagonal", () => {
@@ -76,6 +94,16 @@ describe("diagonal", () => {
         expect(pts[0]!).toEqual({ x: 501, y: 501 });
         expect(pts.at(-1)!).toEqual({ x: 750, y: 750 });
     });
+
+    test("loopPath ramps both axes forever at a fixed step", () => {
+        const pts = take(diagonal.loopPath!(ctxOf({ start: { x: 100, y: 200 } })), 3);
+        // Both axes advance by DIAGONAL_LOOP_STEP (4) each step.
+        expect(pts).toEqual([
+            { x: 104, y: 204 },
+            { x: 108, y: 208 },
+            { x: 112, y: 212 },
+        ]);
+    });
 });
 
 describe("jitter", () => {