Two-stage serve aim: hold + drag shows the reticle, release fires

Flick-to-aim was aim-by-faith — you learned where you aimed after the ball
was gone. Now, at a serveable pretoss, touching and dragging shows a LIVE
reticle (same mapping: direction + length = landing point); release serves
there. The magnet is finally visible: within zSnap the ring turns red and
rides the locked zombie (plus a marker over its head) — you see the lock
BEFORE you commit the tin.

- Context locked at touchstart: a movement drag started mid-rally never
  morphs into a serve when the ball dies (sub-300ms releases still count
  as the rapid flick re-serve — the Phase 1 cadence survives)
- Drag back home = cancel: no serve, the tin stays in stock
- Aimed (drag) serves commit specials at fixed 0.62 quality; the tap-toss
  ritual keeps the PERFECT-timing power ceiling and the stock — placement
  vs power is now a real choice
- Rally / horde / machine gun untouched: drag steers, flick swings
- Serve prompt: 'TAP TO SERVE - HOLD + DRAG TO AIM' / 'AIMED SERVES FIRE
  THE BOMB - TAP KEEPS IT'

Verified with synthetic touch sequences: drag arms the reticle without
serving and it tracks the thumb; release serves at the marker with the bomb
committed; cancel keeps the tin; rally-started drags never morph; locked
reticle renders red on the zombie (screenshot); tennis 12/12; no console
errors.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

state.js

@@ -40,6 +40,7 @@ export const G = {
   deliveries: 0,      // tins delivered this run — indexes the weapon ladder
   tinDue: false,      // the rules called for new balls — deliver at the next changeover
   pendingGame: false, // a game just ended — flash 'GAME N' when the next one arms
+  aim: null,          // live two-stage serve aim {fx, fy, mag} while the thumb is down (splatter pretoss)
   interlude: false,   // sudden-death point vs the racket zombie: tennis rules apply, shamblers spectate
   horde: null,        // active horde wave {t, spawnT, mgT} — machine-gun racket, no serving
   runGames: 0,        // games finished this run (either side) — the difficulty director