Remove unusable Casino building identifier

[diffuin]

Requested by @ifBars in #270.

Diffuin response

Confidence: High

Removed the unusable S1API.Map.Buildings.Casino identifier and its catalog entry. This deliberately breaks source and binary compatibility for mods that reference Buildings.Casino, as authorized, and fully resolves issue #270 without adding an unverified replacement abstraction.

Recommended next steps

1. Removed the misleading public type instead of adding an unrelated interior abstraction.
2. Did not add a catalog test because the existing unit-test harness cannot establish native scene resolution without a game runtime.

Evidence and validation

Evidence inspected

• Building registers and falls back only to NPCEnterableBuilding instances for both target configurations.
• Regular and beta stripped sources declare NPCEvent_StayInBuilding.Building and Dealer.Home as NPCEnterableBuilding.
• The Casino identifier and Casino entry in S1API/Map/Buildings/Buildings.md were the only typed-building catalog references removed.
• Issue [BUG] Casino typed Building identifier cannot resolve through the NPC building registry #270 and its comments were reviewed; the maintainer explicitly requested removal.

Validation performed

• Ran git diff --check.
• Confirmed no remaining typed Casino building references under S1API or S1API.Tests.
• Reviewed the final two-file diff.

Runtime validation remaining

• MonoMelon and Il2CppMelon restore, build, and test were not run because dotnet is unavailable in this checkout environment.
• Human in-game validation remains for Mono and IL2CPP; no Unity, gameplay, schedule, save/load, or multiplayer runtime claim was made.

Diffuin run details

• Provider: codex
• Model: gpt-5.6-terra
• Reasoning: high (Luna advisor: balanced (high); baseline bounded implementation)
• Elapsed: 187s
• Codex thread: 01a002e2-9500-7273-add2-0ac49069f28a

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AI notice: Generated with AI assistance and not guaranteed accurate. Verify findings and plans against the current source and runtime.

Closes #270

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Diffuin job: 69623915-65be-49cf-a513-d9b330ebb0ef
Commit: 3f7884bf33fa2dd2d09f2ead82ef6668c5f17fa3

[ifBars]

@Diffuin It may be better for us to make it obsolete/deprecated to avoid breaking old mods

[diffuin]

I updated this pull request with commit 896ae12.