Bones: client-side SetupBones/studiohdr groundwork

- bones.cpp: resolve IClientRenderable via IClientUnknown slot 6, validate it
  against IVModelInfo GetModel, call SetupBones (slot 16) with engine Time()
  (slot 14), and parse the studio header (GetStudiomodel, slot 29) for
  bones/bone names/parents and hitboxes
- cache up to 64 entity bone snapshots, refreshed at ~30 Hz
- helpers: bone_find/parent/pos, hitbox_center (e.g. "head")
- debug probe: HL2H_BONE_DEBUG=1 draws a white marker at each NPC's head
  hitbox center and logs bone count/head position once

1 files changed, 29 insertions, 0 deletions

diff --git a/src/esp.cpp b/src/esp.cpp
index 4462f07..b384bc4 100644
--- a/src/esp.cpp
+++ b/src/esp.cpp
@@ -3,6 +3,7 @@
 #include <cmath>
 #include <cstring>
 #include <cstddef>
+#include <cstdlib>
 #include <ctime>
 
 static constexpr float PI_F = 3.14159265358979323846f;
@@ -16,6 +17,7 @@ enum SurfSlot {
 enum { LIFE_ALIVE = 0 };
 
 struct EspTarget {
+  int idx;
   float sx, sy;       // screen pos of feet
   float h;            // box height px
   float health, maxhealth;
@@ -242,6 +244,7 @@ static void esp_collect(int local_idx) {
     if (sx < -(float)g_scr_w || sx > 2.0f * (float)g_scr_w) continue;
 
     EspTarget &t = g_targets[g_ntargets++];
+    t.idx = idx;
     t.sx = sx; t.sy = sy; t.h = h;
     t.health = hp > 0 ? (float)hp : 0.0f;
     t.maxhealth = maxhp > 0 ? (float)maxhp : 100.0f;
@@ -319,4 +322,30 @@ void esp_draw() {
     if (esp_option(ESP_OPT_SHOW_NAME))
       draw_text_col(left, top - 14, t.name, 255, 255, 255);
   }
+
+  // Groundwork probe: HL2H_BONE_DEBUG=1 draws a white marker at each NPC's
+  // "head" hitbox center (from SetupBones + studio hitboxes).
+  static bool bone_debug = getenv("HL2H_BONE_DEBUG") != nullptr;
+  if (bone_debug) {
+    static bool head_logged = false;
+    for (int i = 0; i < g_ntargets; i++) {
+      const EspTarget &t = g_targets[i];
+      void *ent = entitylist_get(t.idx);
+      if (!ent || !bones_update(t.idx, ent))
+        continue;
+      Vector head;
+      if (!hitbox_center(t.idx, "head", head))
+        continue;
+      float hx, hy;
+      if (!world_to_screen(head, hx, hy))
+        continue;
+      surf_color(255, 255, 255, 255);
+      surf_rect(1, (int)hx - 2, (int)hy - 2, (int)hx + 3, (int)hy + 3);
+      if (!head_logged) {
+        head_logged = true;
+        logf("bone debug: idx=%d bones=%d head=(%.1f %.1f %.1f)", t.idx,
+             bones_count(t.idx), head.x, head.y, head.z);
+      }
+    }
+  }
 }