plan(G.3a): core teleport-into-dungeon implementation plan (#133)

TDD plan for the gated G.3a core: a pure TeleportArrivalController state machine
(hold-until-hydration + force-snap on impossible/timeout) + its GameWindow wiring
(replace the unconditional arrival snap with recenter + deferred BeginArrival;
per-frame Tick; readiness predicate reusing the #107 login triplet) + the EnvCell
physics/visibility hydration decouple + the visual acceptance gate. G.3b/c/d get
their own plans after the gate.

Also syncs the spec: the readiness predicate reuses SampleTerrainZ + IsSpawnCellReady
+ IsSpawnClaimUnhydratable (the validated #107 login gate) rather than a new
IsLandblockApplied query — strictly more faithful, less new surface.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/superpowers/specs/2026-06-13-dungeon-support-design.md

@@ -130,9 +130,12 @@ All five verified against current code this session (high confidence).
   a 5×5 near window; physics ready +1-2 frames.
 - Recenter keeps the old neighborhood until hysteresis unload (NearRadius+2
   demote, FarRadius+2 unload), so the player isn't instantly stranded.
-- **New code needed:** a "destination landblock applied" query + dest-coord
-  validation (reject out-of-world coords — a malformed portal dest would otherwise
-  leave the player in an invisible, unloadable landblock).
+- **New code needed:** reuse the #107 login-gate **terrain-ready signal**
+  `_physicsEngine.SampleTerrainZ(x,y) is not null` (non-null once the destination
+  terrain landblock has applied) — no separate "landblock applied" query is
+  required. Plus dest-coord validation (reject out-of-world coords — a malformed
+  portal dest would otherwise leave the player in an invisible, unloadable
+  landblock).
 
 ### 2.4 EnvCell hydration coupling (latent landmine — decouple)
 - In `BuildInteriorEntitiesForStreaming` (`GameWindow.cs:5564-5651`), both
@@ -203,17 +206,22 @@ the dungeon cell, on the floor, with walls blocking — no ocean, no ACE
      via the safety-net demote (loud log), exit PortalSpace.
    - `now > deadline` (timeout, ~10 s) → force-snap via safety-net demote + loud
      log, exit PortalSpace. (See §5 — failure-surfacing, not symptom-masking.)
-   - `IsLandblockApplied(destLb) && IsSpawnCellReady(destCell)` → ready: go to 3.
+   - `SampleTerrainZ(destPos) != null && (outdoor || IsSpawnCellReady(destCell))`
+     → ready: go to 3.
    - else stay frozen, retry next frame.
 3. `Placing`: call the **existing** `Resolve(destPos, destCell, Vector3.Zero, …)`.
    Because the cell is now hydrated, Resolve takes the #111 validated-claim branch
    → `WalkableFloorZNearest` grounds the player on the EnvCell floor. Snap entity
    + controller (existing `:4935-4939` code), exit PortalSpace, resume input.
 
-**New streaming query — `IsLandblockApplied(uint landblockId)`** (on
-`StreamingController` / `GpuWorldState`): true once the landblock's terrain has
-been applied (AABB set in `ApplyLoadedTerrainLocked`) **and** `AddLandblock` has
-run into physics. Gate the hold on this, not on the GPU mesh alone.
+**Readiness predicate — reuse the #107 login triplet (no new query).** The
+hold gates on exactly the three checks the login auto-entry gate already uses
+(`GameWindow.cs:1010-1024`), evaluated against the teleport's `(destPos,
+destCell)` instead of the spawn claim: `SampleTerrainZ(destPos.X, destPos.Y) is
+not null` (destination terrain applied) ∧ (outdoor cell OR
+`IsSpawnCellReady(destCell)`); `IsSpawnClaimUnhydratable(destCell)` short-circuits
+an impossible claim to immediate placement. This reuses proven, validated code
+rather than introducing a parallel "landblock applied" query.
 
 **Dest-coord validation:** in `OnLivePositionUpdated`, reject a destination whose
 `(lbX, lbY)` is out of the world grid before recenter; log + abort the teleport
@@ -288,7 +296,7 @@ command bus.
 2. fake UpdatePosition(destCell) → validate dest coords → recenter streaming to dest lb
                                    → prioritize-load dest lb → re-send LoginComplete
 3. HOLD (TeleportArrivalController.Tick, each frame in PortalSpace):
-     ready = IsLandblockApplied(destLb) && IsSpawnCellReady(destCell)
+     ready = SampleTerrainZ(destPos) != null && (outdoor || IsSpawnCellReady(destCell))
      - not ready  → stay frozen, retry   [G.3c: tunnel holds in TAS_TUNNEL/_CONTINUE]
      - impossible → IsSpawnClaimUnhydratable → safety-net demote + loud log
      - timeout    → force-snap + loud log + leave PortalSpace
@@ -374,7 +382,7 @@ visual gate.
 | Unit | Location | Does | Depends on |
 |---|---|---|---|
 | `TeleportArrivalController` | `AcDream.App/World/` | Owns the `Idle/Holding/Placing` phase + `_pendingArrival`; decides hold-vs-place each frame | readiness predicate (injected), `Resolve` (injected), PortalSpace state |
-| readiness predicate | `StreamingController` + `PhysicsEngine` | `IsLandblockApplied(lb)` ∧ `IsSpawnCellReady(cell)`; `IsSpawnClaimUnhydratable(cell)` | dat `LandBlockInfo`, `DataCache` |
+| readiness predicate | `PhysicsEngine` (reused #107 triplet) | `SampleTerrainZ(pos)` ∧ (outdoor ∨ `IsSpawnCellReady(cell)`); `IsSpawnClaimUnhydratable(cell)` | `DataCache`, dat `LandBlockInfo` |
 | hydration decouple | `GameWindow.BuildInteriorEntitiesForStreaming` | `BuildLoadedCell` + `CacheCellStruct` gated on cellStruct/BSP, not render mesh | `cellStruct`, `PhysicsBSP` |
 | `TeleportAnimState` FSM (G.3c) | `AcDream.App` UI/render | Portal-tunnel fade FSM; hold-exit gated on the readiness predicate | `m_pPortalSpace` viewport, the readiness predicate |
 | recall builders (G.3d) | `AcDream.Core/Network/Actions` | Zero-payload outbound game actions | command bus |
@@ -419,7 +427,8 @@ visual gate.
    (`IsSpawnClaimUnhydratable`); hold plausible-but-slow with a ~10 s ceiling;
    on timeout force-snap + loud log (fail visibly, never freeze).
 3. **Big-jump streaming?** Verified to work (Chebyshev recenter). Add only
-   `IsLandblockApplied` + dest-coord validation.
+   dest-coord validation; the readiness gate reuses `SampleTerrainZ` (no new
+   streaming query).
 4. **EnvCell placement vs flat terrain?** The #111 `WalkableFloorZNearest` EnvCell
    path (identical to the cellar path that already works); the flat terrain
    renders below. The gate guarantees the cell is hydrated before Resolve runs.