examples/pong: production-quality Pong game with powerups and multi-ball

A complete, playable Pong game split across examples/pong/*.ne files
and pulled in from a top-level examples/pong.ne. Features:

- **Title screen** with a 3-option menu (CPU VS CPU / 1 PLAYER /
  2 PLAYERS), a cursor sprite, blinking "PRESS A" prompt, brisk
  title march on pulse 2, and autopilot that auto-confirms CPU VS
  CPU after 45 frames of no input so the headless jsnes golden
  harness reaches gameplay by frame 180.

- **Ball physics** with signed-magnitude velocity (u8 magnitude +
  sign bit per axis), wall bounce at top/bottom, paddle AABB
  collision with push-out, and score-out detection at left/right
  exits.

- **Multi-ball** via parallel ball_* arrays (MAX_BALLS = 3). Each
  ball scores a point independently; the round continues until the
  last ball exits the playfield.

- **CPU AI** that tracks the nearest active ball heading toward its
  side with a per-frame step, 4 px dead zone, and CPU_SPEED = 1 so
  rallies can end naturally.

- **Three powerup types** that spawn every ~4 seconds, bounce off
  all four walls, and are caught by paddle AABB overlap:
  1. LONG — extends the catching paddle from 24 → 40 px for 5 hits
  2. FAST — doubles ball x-velocity on the catcher's next hit
  3. MULTI — spawns two extra balls on the catcher's next hit

- **Victory** at first-to-7 with a "PLAYER N WINS" banner and the
  builtin fanfare, auto-returning to Title.

- **Audio**: 5 user-declared sfx (WallBounce, PaddleHit, Score,
  PowerSpawn, PowerCatch) plus a title march and the builtin
  fanfare for victory.

Source layout mirrors examples/war:

    examples/pong.ne               top-level game shell
    examples/pong/PLAN.md          living design doc
    examples/pong/constants.ne     layout + gameplay constants
    examples/pong/assets.ne        45-tile Tileset (paddles, ball, alphabet,
                                   digits, cursor, center-line, powerup icons)
    examples/pong/audio.ne         sfx + music declarations
    examples/pong/state.ne         all mutable globals
    examples/pong/rng.ne           8-bit Galois LFSR
    examples/pong/render.ne        draw helpers
    examples/pong/input.ne         paddle step (human + CPU AI)
    examples/pong/ball.ne          multi-ball physics + paddle collision
    examples/pong/powerup.ne       powerup entity (spawn, bounce, catch, apply)
    examples/pong/title_state.ne   state Title + menu
    examples/pong/play_state.ne    state Playing (P_SERVE/P_PLAY/P_POINT)
    examples/pong/victory_state.ne state Victory

Verification:
- 616 compiler unit tests pass (cargo test --all-targets)
- cargo fmt / cargo clippy --all-targets -- -D warnings clean
- 33/33 emulator harness goldens match
- examples/pong.nes builds byte-identically from source

https://claude.ai/code/session_0134F5uwDEVTes2Ee9S7JeXy

examples/README.md

@@ -38,6 +38,7 @@ Open any `.nes` file in an NES emulator ([Mesen](https://www.mesen.ca/), [FCEUX]
 | `platformer.ne` | **every subsystem** | End-to-end side-scrolling demo: custom CHR tileset, full 32×30 nametable with per-region attribute palettes, 2×2 metasprite hero with gravity/jump physics, wrap-around horizontal scrolling, stomp-or-die enemy collisions with a live stomp-count HUD, coin pickups, user-declared SFX + music, and a Title → Playing → GameOver state machine with a proximity-based autopilot so the headless harness cycles through stomp, stomp, die, and retry inside six seconds. Regenerate the tile art with `cargo run --bin gen_platformer_tiles`. |
 | `sprite_flicker_demo.ne` | `cycle_sprites`, 8-per-scanline hardware limit | Twelve sprites packed onto the same 4-pixel band — two more than the NES's 8-sprites-per-scanline hardware budget. The W0109 analyzer warning fires at compile time, and a `cycle_sprites` call at the end of `on frame` rotates the OAM DMA offset one slot per frame so the PPU drops a *different* sprite each frame. The permanent-dropout failure mode becomes visible flicker, which the eye reconstructs across frames. The classic NES technique used by Gradius, Battletoads, and every shmup that ever existed. |
 | `war.ne` | **production-quality card game**, multi-file source layout | A complete port of the card game War, split across `examples/war/*.ne` files and pulled in via `include` directives. Title screen with a 0/1/2-player menu (cursor sprite, blinking PRESS A, brisk 4/4 march on pulse 2), a 50-frame deal animation, a deep `Playing` state with an inner phase machine (`P_WAIT_A`/`P_FLY_A`/.../`P_WAR_BANNER`/`P_WAR_BURY`/`P_CHECK`), card-conserving queue-based decks built on a 200-iteration random-swap shuffle, a "WAR!" tie-break that buries 3+1 face-down cards per player and plays a noise-channel thump per bury, and a victory screen with the builtin fanfare. The first NEScript example to use a top-level file as a thin shell that `include`s ~12 component files; building it surfaced seven compiler bugs across the analyzer, IR lowerer, and codegen that were all fixed on the same branch (see `git log` for details). |
+| `pong.ne` | **production-quality Pong**, powerups, multi-ball, multi-file | A complete Pong game split across `examples/pong/*.ne`. CPU VS CPU / 1 PLAYER / 2 PLAYERS title menu with brisk pulse-2 title march and autopilot, smooth ball physics with wall and paddle bouncing, CPU AI that tracks the ball with a reaction lag and dead zone, three powerup types (LONG paddle for 5 hits, FAST ball on next hit, MULTI-ball on next hit spawning 3 balls) that bounce around the field and are caught by paddle AABB overlap, multi-ball scoring (each ball scores a point, round continues until last ball exits), inner phase machine (`P_SERVE`/`P_PLAY`/`P_POINT`), and a "PLAYER N WINS" victory screen with the builtin fanfare. First-to-7 wins. |
 
 ## Emulator Controls