Add pluggable movement strategies (v1.3.0)

Turn the hardcoded straight-line sweep into a strategy system behind three
seams so new patterns are easy to add and, for the first time, testable
without nut.js or a real screen:

- src/device.ts:     injectable Device seam over nut.js (autoDelayMs lives
                     here now); the only module that touches the native lib.
- src/strategies.ts: pure per-pattern path generators + registry + lenient
                     name resolution. Ships line, diagonal, jitter, walk,
                     arc, figureEight.
- src/executor.ts:   single executePath driver owning bounds policy
                     (abort/clamp/reflect), pacing, interrupt detection, and
                     restore-on-clean.

keeper.ts's simulateActivity now selects a strategy and delegates to the
executor; the default `line` pattern is byte-for-byte the previous behavior.

New config surface, layered CLI > file > default with strict validation:
- -p/--pattern <name>   movement strategy (names matched case/-/_-insensitive)
- -s/--step-size <px>   pixels per step; stepCount is now a step *count*

Robustness for the new edge-seeking patterns: interrupt detection compares
against the last commanded (rounded) point with a 2px tolerance, and
clamp/reflect stay a couple pixels off the screen edge, so sub-pixel cursor
placement on scaled/multi-monitor displays isn't misread as user activity.
jitter's radius scales with sweep length so it moves at the default stepSize.

Tests: new suites for strategies, the executor (all bounds policies,
rounding, interrupt, tolerance, pacing), and the keeper loop; config and
configFile suites extended for pattern/stepSize. editor.test.ts moved to
tests/ for consistency. 64 pass.

src/cli.ts

@@ -16,7 +16,9 @@
  *   -m, --move-interval     Idle time (seconds) before a sweep fires.
  *   -c, --check-interval    Cursor poll cadence (seconds).
  *   -d, --step-delay        Pause between synthetic steps (ms).
- *   -n, --step-count        Steps per sweep (pixels).
+ *   -n, --step-count        Steps per sweep (count).
+ *   -s, --step-size         Pixels moved per step.
+ *   -p, --pattern           Movement strategy name (see strategies.ts).
  *   -V, --verbose           Enable per-sweep / interrupt / bounds logging.
  *                           (`-V` capital because `-v` is `--version`.)
  *
@@ -31,6 +33,7 @@ import { parseArgs } from "node:util";
 
 import { DEFAULT_CONFIG, defaultConfigPath } from "./config.ts";
 import { CliError } from "./errors.ts";
+import { PATTERN_NAMES, resolvePatternName } from "./strategies.ts";
 
 /**
  * Result of `parseCliArgs`. Numeric fields are `undefined` when the user
@@ -45,7 +48,10 @@ export interface ParsedCliArgs {
     moveInterval: number | undefined;   // seconds
     checkInterval: number | undefined;  // seconds
     stepDelay: number | undefined;      // milliseconds
-    stepCount: number | undefined;      // pixels
+    stepCount: number | undefined;      // count
+    stepSize: number | undefined;       // pixels
+    /** Movement strategy name, validated against the registry. */
+    pattern: string | undefined;
     /**
      * `true` when `-V`/`--verbose` was passed; `undefined` when it was not.
      * `undefined` (not `false`) lets the layered resolver distinguish "user
@@ -69,6 +75,20 @@ function parsePositiveNumber(name: string, raw: string | undefined): number | un
     return n;
 }
 
+/**
+ * Validate a CLI-supplied movement-pattern name. Returns `undefined` when
+ * the flag was not supplied; throws `CliError` naming the valid patterns
+ * when the value isn't a registered strategy.
+ */
+function parsePatternName(raw: string | undefined): string | undefined {
+    if (raw === undefined) return undefined;
+    const canonical: string | null = resolvePatternName(raw);
+    if (canonical === null) {
+        throw new CliError(`invalid value for --pattern: '${raw}' (valid: ${PATTERN_NAMES.join(", ")})`);
+    }
+    return canonical;
+}
+
 /**
  * Parse `process.argv` into a typed `ParsedCliArgs`. Uses Node's built-in
  * `parseArgs` in strict mode so unknown flags and missing values surface
@@ -88,6 +108,8 @@ export function parseCliArgs(): ParsedCliArgs {
                 "check-interval": { type: "string",  short: "c" },
                 "step-delay":     { type: "string",  short: "d" },
                 "step-count":     { type: "string",  short: "n" },
+                "step-size":      { type: "string",  short: "s" },
+                pattern:          { type: "string",  short: "p" },
                 verbose:          { type: "boolean", short: "V" },
             },
             strict: true,
@@ -110,6 +132,8 @@ export function parseCliArgs(): ParsedCliArgs {
         checkInterval: parsePositiveNumber("check-interval", values["check-interval"] as string | undefined),
         stepDelay:     parsePositiveNumber("step-delay",     values["step-delay"]     as string | undefined),
         stepCount:     parsePositiveNumber("step-count",     values["step-count"]     as string | undefined),
+        stepSize:      parsePositiveNumber("step-size",      values["step-size"]      as string | undefined),
+        pattern:       parsePatternName(values.pattern as string | undefined),
         verbose:       values.verbose === true ? true : undefined,
     };
 }
@@ -152,7 +176,10 @@ Options:
   -m, --move-interval <seconds>   Idle time before a sweep fires. Default: ${moveDefaultSec}.
   -c, --check-interval <seconds>  Cursor poll cadence. Default: ${checkDefaultSec}.
   -d, --step-delay <ms>           Pause between synthetic steps. Default: ${DEFAULT_CONFIG.stepDelay}.
-  -n, --step-count <pixels>       Steps per sweep. Default: ${DEFAULT_CONFIG.stepCount}.
+  -n, --step-count <count>        Steps per sweep. Default: ${DEFAULT_CONFIG.stepCount}.
+  -s, --step-size <pixels>        Pixels moved per step. Default: ${DEFAULT_CONFIG.stepSize}.
+  -p, --pattern <name>            Movement strategy. Default: ${DEFAULT_CONFIG.pattern}.
+                                  One of: ${PATTERN_NAMES.join(", ")}.
   -V, --verbose                   Log every sweep, interrupt, and bounds event
                                   (default prints only the startup banner).
 
@@ -162,6 +189,7 @@ Examples:
   move
   move --move-interval 180 --check-interval 5
   move -m 300 -V
+  move --pattern arc --step-size 3
   move --config ~/myprofile.json
 `);
 }