Add random pattern selection (-r / --pattern random)

Pick a different movement pattern every time a sweep is triggered, so the
motion varies across the day instead of repeating one shape.

- strategies.ts: add the `random` sentinel, `SELECTABLE_PATTERN_NAMES`,
  `isSelectablePattern`, and `createRandomPicker`. `random` is deliberately
  NOT a registry entry: it has no path of its own, so `STRATEGIES` stays a
  total lookup and `PATTERN_NAMES` keeps listing only real generators. The
  picker is a closure over `last`, giving a uniform draw that never returns
  the same pattern twice in a row. Building CANONICAL_PATTERNS from the
  selectable list makes both validation boundaries accept `random` (and
  loose spellings) for free, and extends the normalization-collision
  assertion to cover the sentinel.
- cli.ts: add `-r`/`--random` plus an exported `selectPattern` holding the
  conflict rule. `-r` is sugar for `--pattern random`, so the two agreeing
  is a no-op while `-r -p arc` is rejected as contradictory. The flag folds
  into `pattern`, so ConfigOverrides, resolveConfig, and move.ts are
  untouched. `parseCliArgs` now takes its argv as an optional parameter so
  the flag surface is testable without process.argv.
- keeper.ts: resolve `random` via the picker once per trigger, before the
  loop-mode branch, so a pick holds for a whole loop run rather than
  changing mid-run. runKeeper builds one picker for the process, so the
  no-repeat memory spans sweeps minutes apart. Because the pick is a real
  strategy, --verbose logs the concrete pattern name and a pick with an
  infinite loopPath still bounces edge-to-edge under --loop.
- config.ts / configFile.ts: accept the sentinel where a pattern is valid,
  and quote the selectable list in errors. No `random` boolean config key —
  the file spells it "pattern": "random".

executor.ts and move.ts needed no changes.

Tests: new tests/cli.test.ts (the file had no coverage before) covering the
flag surface and the conflict rule; picker tests pinning the no-repeat and
full-registry-coverage properties; keeper tests pinning once-per-trigger and
once-per-loop-run.

CHANGELOG.md

@@ -5,6 +5,35 @@ All notable changes to `move` are documented here.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [Unreleased]
+
+### Added
+- Random pattern selection: `-r` / `--random`, and `random` as a value for
+  `--pattern` and the `pattern` config key. Every time a sweep is triggered,
+  a different movement pattern is chosen, so the motion varies across the day
+  instead of repeating one shape. Two rules keep it predictable: the same
+  pattern is never chosen twice in a row, and the pick happens once per
+  trigger — in loop mode it holds for the whole loop run rather than changing
+  mid-run. The pick is a real strategy, so `--verbose` logs the concrete
+  pattern name and a pick with an infinite loop path (`line`, `diagonal`)
+  still bounces edge-to-edge under `--loop`.
+
+  `-r` is defined as sugar for `--pattern random`, so passing both is
+  rejected (exit `2`) unless they agree: `move -r -p arc` is an error, while
+  `move -r -p random` is a no-op. There is no `random` boolean config key —
+  the file spells it `"pattern": "random"`.
+
+  `random` is deliberately not a registry entry: it has no path of its own,
+  and the keeper resolves it to a real strategy per sweep. `PATTERN_NAMES`
+  therefore still lists only real generators, with the new
+  `SELECTABLE_PATTERN_NAMES` covering what a user may select.
+
+### Changed
+- `parseCliArgs` now takes its argument list as an optional parameter
+  (defaulting to the real command line), so the flag surface is unit-testable
+  without touching `process.argv`. Adds `tests/cli.test.ts`, which previously
+  had no coverage.
+
 ## [1.4.0] - 2026-08-17
 
 ### Added