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.

src/configFile.ts

@@ -12,6 +12,7 @@
  *   stepDelay      number   milliseconds, positive
  *   pattern        string   a registered strategy name
  *   verbose        boolean
+ *   loop           boolean
  *
  * Unknown keys, wrong types, and non-positive numerics are rejected with a
  * `CliError` so the entry point can exit 2 (user error) with a clear
@@ -39,6 +40,7 @@ const ALLOWED_KEYS: ReadonlySet<string> = new Set<string>([
     "stepDelay",
     "pattern",
     "verbose",
+    "loop",
 ]);
 
 /**
@@ -173,5 +175,9 @@ export function loadConfigFile(explicitPath: string | undefined): ConfigOverride
             "verbose" in parsed
                 ? requireBoolean("verbose", parsed.verbose, path)
                 : undefined,
+        loop:
+            "loop" in parsed
+                ? requireBoolean("loop", parsed.loop, path)
+                : undefined,
     };
 }