tests, docs: cover world.talk and link.battle_ended

gate_meta_coverage asks every extension point for a unit test through the
public mod API, a no-mod parity test, and docs. The seams commit shipped the
call sites and owed the rest.

Both cases drive the real engine path, and both assert the unhooked build
first, so they fail if the seam is deleted and if it changes vanilla
behaviour. world_talk stands an object on the faced cell: with no mod the A
press reaches talkTo, with a mod that owns the object it does not, and an
object the mod ignores still falls through. link_battle_ended parks a
session at the end of a battle and checks the event carries the result, the
role, and both party copies.

The parity side needed nothing. gate_hooks and gate_events walk the live
catalog, so both seams were covered structurally as soon as the call sites
existed.

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

docs/modding.md

@@ -265,6 +265,80 @@ Red exposes FLY separately because it requires a destination picker:
 and `mod.world:flyTo(mapId)` accepts only a visited destination from the native
 Fly town list. Gold does not expose these two methods yet.
 
+## Self-driven world actors
+
+`mod.world:spawnNpc()` returns a handle whose `scriptMove` queues onto the
+overworld's scripted-movement list. A non-empty list is how the overworld
+knows a cutscene is running, so it gates player input for as long as the
+actor walks -- right for Oak marching to his lab, wrong for an actor that
+moves on its own schedule (a networked player's ghost, an ambient walker).
+Five handle methods drive one without that lockout:
+
+```lua
+local ghost = mod.world:spawnNpc({ map = "ROUTE_1", x = 5, y = 7,
+                                   sprite = "SPRITE_RED" })
+if ghost:canStep("up") then ghost:stepNow("up") end   -- one tile, now
+if not ghost:isMoving() then ghost:placeAt(9, 3, "down") end  -- snap, no walk
+ghost:setPassable(true)                               -- walk-through
+```
+
+`stepNow(dir)` sets the same per-tile state `scriptMove` does, minus the
+queue. It deliberately does **not** check collision: a caller replaying a
+move that was already decided elsewhere (validated on a peer's machine, or
+authored) would let the two copies disagree about where the actor is if this
+re-judged it. Ask `canStep(dir)` first when you do want the map's opinion.
+`placeAt(x, y, facing)` snaps with no animation and clears any step in
+flight, for a warp arrival or a resync too far gone to walk off.
+`isMoving()` lets a driver pace itself instead of stomping a move already
+running. `setPassable(flag)` is the flag `Collision.occupied` skips (the
+engine's own user is Yellow's companion Pikachu); a passable object still
+draws and can still be talked to.
+
+An object spawned this way carries no `TEXT_*` id, so the vanilla talk path
+has nothing to say for it. The **`world.talk`** hook is the A press on an
+object, raised before the map's text tables get it:
+
+```lua
+mod.hooks:wrap("world.talk", function(next, ow, target)
+  if mine(target) then
+    say(target)        -- the mod answers for an object it owns
+    return             -- ...by not calling next()
+  end
+  return next(ow, target)   -- everything else falls through unchanged
+end)
+```
+
+With no subscriber the A press reaches `talkTo` exactly as before. An object
+mid-step raises no hook, matching the vanilla gate.
+
+## Adopting an already-paired link session
+
+`LinkState.newFromSession(game, transport, mode, isHost, opts)` starts a link
+session on a transport that is *already* paired, skipping the address/code
+entry UI while keeping the hello and fingerprint compatibility exchange
+intact. `transport` is anything `Session` accepts, which is what lets a mode
+tunnel a battle through its own connection rather than opening a second one.
+
+When the battle finishes, **`link.battle_ended`** reports the outcome:
+
+```lua
+mod.events:on("link.battle_ended", function(ev)
+  -- ev = { result, myParty, theirParty, peerName, role }
+end)
+```
+
+The party copies are the point. Cable rules leave the real party untouched,
+so a mode built on link battles -- a tournament ladder, a battle royale --
+has no other way to learn what the fight cost, and by the time the state
+unwinds the battle object is gone. `role` is `"host"` or `"guest"`.
+
+Two smaller pieces support the same shape of mode. `Game:startNewGame(opts)`
+is the title screen's NEW GAME closure made callable, with `opts.intro =
+false` to land straight in the world -- a mode that hands out its own starting
+state has no use for Oak's speech. `CodeEntry.new` takes an optional
+`{ length = , charset = }`, so the slot-scrub widget that enters a link code
+can also carry a room code or an address.
+
 ## Read-only battle snapshots
 
 `mod.battle:snapshot()` returns `nil` outside a battle and a copied battle