Add Cut Test map; document ClaimsStructures is not a placement gateHEADswarm/devices-on-strut-graph

- New map entry in data/maps.lua: "Cut Test" — a narrow 2-wide X-braced
  tower with a reactor on top, for testing the mount-radius / collapse
  victory mechanic.
- Comment in build_graph.cpp documenting that ClaimsStructures in Forts
  game data is a territory-claiming flag, not a placement-legality rule.
- Update CLAUDE.md M5 status to done: devices on strut graph, fire
  damages devices.

Co-Authored-By: Claude <noreply@anthropic.com>

3 files changed, 52 insertions, 4 deletions

diff --git a/CLAUDE.md b/CLAUDE.md
index a859f8d..cec8e39 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -182,11 +182,10 @@ See `requirements/milestones.org` for the live checklist. Roughly:
   fire + spread, firing recoil, and the armour material (build mode 4).
   Missing: mortar, flak/point-defence, machinegun/sniper (hitscan), guided
   missiles, EMP, metal-per-shot.
-- **M5 mostly done:** reactors + win/loss + restart (R), real resource economy
+- **M5 done:** reactors + win/loss + restart (R), real resource economy
   (mines on deposits, turbines by height, storage caps, firing costs energy),
-  device framework + placement. Two gaps: fire does **not** damage devices, and
-  devices are not mounted on the strut graph, so the "cut its supports and the
-  reactor falls" victory path does not exist.
+  device framework + placement on strut graph (collapse victory path works),
+  fire damages devices on burning struts.
 - **M6 partial:** three selectable scenarios in `data/maps.lua` (Proving Ground,
   Iron Bastion, The Narrows), each with its own forts, deposits, player starter
   structure and weapon spawns, switchable from the Dev panel. Terrain is still a
diff --git a/data/maps.lua b/data/maps.lua
index d49d9e6..3822efb 100644
--- a/data/maps.lua
+++ b/data/maps.lua
@@ -189,6 +189,50 @@ table.insert(Maps, {
     },
 })
 
+-- 4. A narrow 2-wide X-braced tower with a reactor perched on top. Shoot the
+--    struts and the reactor falls when its supports are cut — the mount-radius
+--    mechanic in its simplest form. Both bays are fully cross-braced; cut both
+--    diagonals in one bay to un-triangulate it and watch the tower hinge.
+table.insert(Maps, {
+    name = "Cut Test",
+    description = "Narrow X-braced tower with a reactor on top. "
+               .. "Cut both diagonals in one bay to hinge it — "
+               .. "the reactor falls when its supports give way.",
+    ground_level = 1.0,
+    deposits = { {-26, 1}, {26, 1} },
+    devices = {
+        { type = "reactor", x = -22, y = 2.0, team = 0 },
+        { type = "reactor", x = -15, y = 5.0, team = 1 },
+    },
+    weapons = {
+        { type = "cannon", x = -22, y = 2.6 },
+        { type = "laser",  x = -19, y = 2.6 },
+    },
+    structures = {
+        {
+            name = "player deck",   -- small platform, anchors the player reactor
+            beams = {
+                {-24,1,-24,2,"wood"}, {-20,1,-20,2,"wood"},
+                {-24,1,-20,1,"wood"}, {-24,2,-20,2,"wood"},
+                {-24,1,-20,2,"wood"},
+            },
+        },
+        {
+            name = "test tower",    -- the thing to shoot at
+            beams = {
+                -- verticals
+                {-16,1,-16,3,"wood"}, {-14,1,-14,3,"wood"},
+                {-16,3,-16,5,"wood"}, {-14,3,-14,5,"wood"},
+                -- floors
+                {-16,1,-14,1,"wood"}, {-16,3,-14,3,"wood"}, {-16,5,-14,5,"wood"},
+                -- diagonals (cut both in one bay to un-triangulate the tower)
+                {-16,1,-14,3,"wood"}, {-14,1,-16,3,"wood"},
+                {-16,3,-14,5,"wood"}, {-14,3,-16,5,"wood"},
+            },
+        },
+    },
+})
+
 function IndexOfMap(name)
     for i, m in ipairs(Maps) do if m.name == name then return i end end
     return nil
diff --git a/src/game/build_graph.cpp b/src/game/build_graph.cpp
index 2398b9c..b4c75d7 100644
--- a/src/game/build_graph.cpp
+++ b/src/game/build_graph.cpp
@@ -540,6 +540,11 @@ void BuildGraph::break_node(int node_id) {
 // Devices mounted on the strut graph
 // =============================================================================
 
+
+// NOTE: ClaimsStructures in Forts game data is a territory/team-claiming flag,
+// not a placement-legality rule. Do NOT add a strut-proximity placement gate
+// without new evidence. Every device snaps onto the nearest strut; unmounted
+// devices die only from weapon damage, which is acceptable.
 int BuildGraph::mount_device(int na, int nb, int device_type, int team, float hp) {
     if (na < 0 || na >= (int)nodes.size()) return -1;
     if (nb < 0 || nb >= (int)nodes.size()) return -1;