fix(camping): half-slab hammock geometry + smarter tent grounding

- Hammock now uses a custom geometry.silverlabs.hammock_slab (8-voxel
  tall half-slab instead of a full cube), matching its thin collision
  box so the block reads visually as a hammock cradle, not a brick.

- Tent placement now projects the player's feet down to the nearest
  solid block (up to 3 blocks) before picking the base Y, so mid-jump
  fractional positions or standing-on-slab cases don't mis-place the
  footprint one block too high.

- Failure messages now include the exact failing cell coordinates and
  the block type that's in the way, so we can diagnose live pitch
  attempts without guesswork.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

camping-supplies-addon/camping_supplies_RP/models/blocks/hammock_slab.geo.json

@@ -0,0 +1,35 @@
+{
+  "format_version": "1.21.0",
+  "minecraft:geometry": [
+    {
+      "description": {
+        "identifier": "geometry.silverlabs.hammock_slab",
+        "texture_width": 16,
+        "texture_height": 16,
+        "visible_bounds_width": 2,
+        "visible_bounds_height": 1,
+        "visible_bounds_offset": [0, 0.25, 0]
+      },
+      "bones": [
+        {
+          "name": "root",
+          "pivot": [0, 0, 0],
+          "cubes": [
+            {
+              "origin": [-8, 0, -8],
+              "size": [16, 4, 16],
+              "uv": {
+                "north": { "uv": [0, 12], "uv_size": [16, 4] },
+                "south": { "uv": [0, 12], "uv_size": [16, 4] },
+                "east":  { "uv": [0, 12], "uv_size": [16, 4] },
+                "west":  { "uv": [0, 12], "uv_size": [16, 4] },
+                "up":    { "uv": [0, 0],  "uv_size": [16, 16] },
+                "down":  { "uv": [0, 0],  "uv_size": [16, 16] }
+              }
+            }
+          ]
+        }
+      ]
+    }
+  ]
+}