docs: record SGS hall POI visibility audit

.superpowers/sdd/task-4-report.md

@@ -0,0 +1,54 @@
+# Task 4: Confirm floor-mode hall POI visibility — Implementation Report
+
+## Status
+**DONE**
+
+## Summary
+Source inspection confirms floor mode already prevents hall POI hiding via distance/limit pruning. No code change required.
+
+## Findings
+
+### Step 1: Floor visibility tier inspection
+Confirmed `getPoiVisibilityTier()` at `src/components/map/ThreeMap.vue:650-651`:
+```ts
+const getPoiVisibilityTier = (): PoiVisibilityTier => {
+  if (activeView.value === 'floor') return 'full'
+```
+
+### Step 2: Visibility tier behavior analysis
+When tier is `'full'`:
+- `getPoiVisibilityLimit('full')` returns `Number.POSITIVE_INFINITY`.
+- `getPoiScreenSpacing('full')` returns `0`.
+
+### Step 3: Pruning mechanism verification
+In `updatePoiVisibilityByDistance()`:
+- `exceedsLimit` is false for `Infinity` because `Number.isFinite(Infinity)` is false.
+- `isTooClose` is false when spacing is 0.
+- `exhibition_hall` and `exhibition_hall_entrance` are in `corePoiCategories`.
+
+### Conclusion
+Floor mode POI visibility is already correctly configured:
+1. Distance pruning is disabled.
+2. Count pruning is disabled.
+3. Hall POIs pass category checks.
+4. Selected/focused POIs always show.
+
+No code modification needed.
+
+## Files Inspected
+- `src/components/map/ThreeMap.vue`
+
+## Commands Run
+None required — source inspection confirms correct behavior.
+
+## Commits Created
+None — no code changes.
+
+## Self-Review
+- Floor mode already returns `'full'` visibility tier.
+- `'full'` tier prevents both distance and count pruning.
+- Hall POIs are included in `corePoiCategories`.
+- Logic is correct and no defensive guard is needed.
+
+## Concerns
+None.