feat(input): press --hold <ms> for precise timed key-holds + document timed-driving pattern

Dogfooding by driving a canvas game surfaced that per-action shell round-trips
(keydown; sleep; keyup) are the slowest, lowest-fidelity way to drive anything
timed — each is a process spawn + relay round-trip with ~250ms jitter, so a
'0.8s hold' is anything but.

- 'press <key> --hold <ms>': keyDown, wait, keyUp all inside the daemon, so the
  hold duration is precise and it's one round-trip. For games (hold-to-move/
  charge) and any press-and-hold.
- Documented the real driving pattern in the core skill + --help: script a timed
  sequence in ONE round-trip with 'batch "press d --hold 900" "press j" "wait 200"'
  (batch sends each step to the running daemon; --hold/wait block in-daemon), and
  prefer reading engine state via main-world 'eval' over guessing from pixels.

Parser test covers plain/held/missing-duration. Builds on the keydown/keyup full
descriptor fix.

cli/src/output.rs

@@ -3070,7 +3070,9 @@ Core Commands:
   dblclick <sel>             Double-click element
   type <sel> <text>          Type into element
   fill <sel> <text>          Clear and fill
-  press <key>                Press key (Enter, Tab, Control+a)
+  press <key> [--hold <ms>]  Press key (Enter, Tab, Control+a). --hold keeps it
+                             down <ms> then releases — precise (in-daemon), for
+                             games/charge: `press d --hold 800`
   keydown <key>              Hold a key down (no auto-release) — for games/shortcuts
   keyup <key>                Release a held key. Pair with keydown to hold-to-move:
                              `keydown d` … `keyup d`