Let NPCs roam as HandleNPCStep does

- Random walks and spins from SpriteMovementData, with random sleeps.
- CanObjectMoveInDirection: side walls, land, objects' current and
  previous tiles, the radius (stored plus one) and the screen edge.
- Objects freeze while text is open and during applymovement, and
  return home when both they and their home leave the object window.
- Wandering positions are not saved; test helpers replan around NPCs.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/PLAN.md

@@ -56,19 +56,20 @@ The emulator-backed prototype is now at `/reference.html`. The default applicati
 - `VAR_BOXSPACE` reads an empty box: nothing can be caught or deposited yet.
 - The battle engine gained `recoil` (Struggle). A local stress run of 360 Route 29 battles across all starters and times of day finishes without refusals.
 - Save format 3 gains `fruitTrees`, `dailyReset` and `lastSpawnMap`; older backups migrate by absence.
+- NPCs roam as `HandleNPCStep` does: random walks (Y, X, XY) and slow/fast spins from `SpriteMovementData`, `CanObjectMoveInDirection` (side walls, land, objects' current and previous tiles, radius stored plus one, screen edge), random sleeps, freezing during text and `applymovement`, and deletion/respawn at home beyond the object window. Wandering positions are not saved; objects start from home on reload.
 - Still refused: the catching tutorial (`catchtutorial`) and Cherrygrove's rival scene, both reachable only after the Mystery Egg errand.
 
 ## In progress: native battles
 
 The battle core, ROM tables, encounter hooks, battle UI and whiteout hooks are present. Unit tests cover wins, escape, loss, experience and move learning; reference tests compare damage and type effectiveness. Browser tests drive a test-only wild encounter through the real UI: victory with level-up and move learning, escape, whiteout, keyboard and on-screen D-pad menu navigation, mid-battle backup restore, and rollback of unsupported effects. Real Route 29 encounters now use the ROM's encounter tables. Capture, switching, items in battle, trainer battles and the rest of the opening quest remain unfinished.
 
-This is still not a complete new game. Party/bag/Pokégear menus, story progression beyond Cherrygrove, NPC roaming, decorations, animated terrain, surfing and audio remain unfinished. Save slots, a Johto/Kanto atlas, Pokédex records, online Link, friends and real-world steps come later.
+This is still not a complete new game. Party/bag/Pokégear menus, story progression beyond Cherrygrove, decorations, animated terrain, surfing and audio remain unfinished. Save slots, a Johto/Kanto atlas, Pokédex records, online Link, friends and real-world steps come later.
 
 ## 1. Complete the overworld foundation
 
 Map headers, location names, connection offsets, connected-border drawing, coordinate events, scene scripts, map callbacks and scripted movement are in place (see above). Next: enable connected transitions as their maps are ported; add dynamic warps, elevators, ice, currents, remaining forced movement, surfing, cycling, cut trees and boulders. Player turn timing still needs a reference comparison.
 
-Port decorations, tile changes (`changeblock`), NPC roaming movement types, trainer sight lines and the remaining movement commands. Complete terrain animation, layering and special palettes. Record deviations from the original until a comparison test closes them.
+Port decorations, tile changes (`changeblock`), the remaining NPC movement types (followers, bouncing, Strength boulders), trainer sight lines and the remaining movement commands. Complete terrain animation, layering and special palettes. Record deviations from the original until a comparison test closes them.
 
 Acceptance: representative outdoor/interior/cave/connected-map traces produce matching positions, collisions, transitions and event changes in native and reference engines. Do not enable an area merely because its image can be decoded.
 
@@ -78,7 +79,7 @@ Introduce native player, party, Pokémon, inventory, money and quest models. Rea
 
 Expand script calls, choices, scene state, inventory commands and native special handlers. Translate routines reached through assembly calls into explicit native services; never fall back to emulator execution in the shipping game.
 
-Meeting Mom, Elm's introduction, the starter, the aide's Potion, Route 29 and Cherrygrove run now. Next: NPC roaming movement, trainer sight lines and trainer battles, Route 30 and Mr. Pokémon, the Mystery Egg round trip with the catching tutorial and the rival battle; then the introduction's naming and clock screens.
+Meeting Mom, Elm's introduction, the starter, the aide's Potion, Route 29 and Cherrygrove run now. Next: trainer sight lines and trainer battles, Route 30 and Mr. Pokémon, the Mystery Egg round trip with the catching tutorial and the rival battle; then the introduction's naming and clock screens.
 
 Complete and validate the native battle engine: deterministic randomness, stats, move selection, accuracy/critical checks, damage, status, turn order, switching, fainting, experience, capture and rewards. Compare controlled seeds and states with the original, including integer rounding and overflow behavior.