## Summary
House customization rejected ~40% of components — all classic/base tiles such as **sandstone** — for non-staff players. The pieces appeared briefly in the editor, then vanished before commit; only staff (GM+) could add them.
## Root cause
A data-convention mismatch introduced when housing.bin support was added (#2329).
- The OSI `housing.bin` encodes pre-AOS base pieces with the client **T2A** feature bit (`0x1`).
- `walls.txt` (and RunUO) encode the same pieces as `FeatureMask = 0` (always valid).
- `ComponentVerification.CheckValidity` validates against `ExpansionInfo.HousingFlags`, whose enum has no `0x1` bit, so base pieces failed `(HousingFlags & 0x1) != 0`.
- `HouseFoundation.Designer_Build` only enforces `ValidPiece` for `AccessLevel < GameMaster`, so staff bypassed validation while players had placements rejected — the server re-sends the design state and the client rebuilds the house from it, erasing the just-placed piece.
This only affects servers loading `housing.bin` from a UOP client; the old txt-only path (pre-#2329, like RunUO) was unaffected because base pieces are `0` there.
## Fix
Normalize the `housing.bin` feature mask to the housing-tier bits on load (`& HousingFlags.HousingEJ`). Base pieces collapse to `0` (always valid, exactly as `walls.txt` encodes them); `AOS`/`SE`/`ML`/... pass through unchanged. Both data sources now produce an identical validity table, matching RunUO behavior. `CheckValidity` and the `val != -1` anti-cheat guard are unchanged.
## Verification
- Parsed the real `housing.bin` from a 7.0.x client: sandstone (`0x345`) loads as `0x1` → `& HousingEJ` → `0` → valid; tier pieces (`0x40` SE, etc.) pass through; unregistered tiles stay `-1` → rejected.
- Confirmed OSI's own files disagree for the same pieces: `walls.txt` base `FeatureMask = 0` vs `housing.bin` `0x1`.
- `dotnet build` clean (0 warnings, 0 errors).
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