Spider webs no longer trampled

[nooga]

The spider webs don't disappear when a creature breaks free. This seems like a regression.

[mparrett]

Confirmed, and it is a regression — root cause below, fix on fix/web-trample.

Diagnosis

Two systems decrement :webbed every turn, and only one of them tramples:

• The struggle branch (world/player-move, ai/try-move) reads the ttl; at ttl ≤ 1 it calls fire/trample-web! and removes the status. Otherwise it writes ttl−1.
• The generic status tick (status/tick-entity-statuses) decrements again the same turn and removes an expired status silently — no trample.

So the ttl drains by 2 per webbed turn, and the web only gets trampled if the struggle read is what hits the bottom:

• ttl 3 (original): the struggle reads 3 and writes 2, the tick drops it to 1; next turn the struggle reads 1 and tramples. Worked.
• ttl 2 (after balance: tame slimes, throttle ranged fire rate, soften spider webs #71 softened the web): the struggle reads 2 and writes 1, then the tick drops it to 0 and silently removes it. Next turn the player walks off free, web intact. The trample branch is unreachable.

#71's one-line change (:webbed 3 to 2) meant "escape one turn
sooner" but crossed the parity threshold where the tick always wins the race.

The monster path has been broken since webs landed (8feaa1c): creature-turn ticks statuses before the action, so at ttl 3 the sequence is tick (3 to 2), struggle (2 to 1), then the tick removes the status at 0 — monsters have never trampled a web.

Fix

Branch fix/web-trample (ca5641c): statuses can declare :no-decay, and :webbed does — the generic tick leaves its ttl to the struggle branches, which own the trample. That fixes both paths and makes the ttl mean what #71 assumed: the number of struggles to break free. Includes regression tests (tick leaves :webbed alone; player break-free leaves ash); the suite is green, and the new tests fail on main.

One behavior note: a webbed creature that never attempts a move (e.g. attacking an adjacent target) now stays webbed until it does — it no longer times out of the web by standing still. That read as correct to me, but it is a balance-visible change.

I'll open the PR from that branch — happy to fold in any changes first.