fix: adjust posecode examples for correct biomechanical form

Author: a-baran-orhan

spec/examples/cobra.posecode

@@ -3,11 +3,11 @@ posecode stretch "Cobra"
   pose start = prone
 
   step "Lift" 2.5s ease-in-out:
-    spine: extend 30
+    spine: extend 25
     chest: extend 15
-    neck: extend 25
-    shoulders: flex 50
-    elbows: flex 25
+    neck: extend 20
+    shoulders: flex 110
+    elbows: flex 40
     reach: hands floor
     cue "Press the palms into the floor and lift the chest, shoulders rolling back"
 

spec/examples/deadlift.posecode

@@ -5,15 +5,19 @@ posecode exercise "Deadlift"
   step "Lower" 1.8s ease-in-out:
     pelvis: hinge 75
     knees: flex 25
+    ankles: plantarflex 25
     shoulders: flex 70
+    elbows: pronate 80
     neck: extend 12
     ground-lock: feet
     cue "Push the hips back and hinge with a flat back: let the arms hang to the bar"
 
   step "Lift" 1.4s ease-out:
     pelvis: hinge 0
     knees: flex 0
+    ankles: plantarflex 0
     shoulders: flex 0
+    elbows: pronate 0
     neck: extend 0
     ground-lock: feet
     cue "Drive the hips forward to stand tall, bar close to the body"

spec/examples/plank-hold.posecode

@@ -2,15 +2,18 @@ posecode posture "Plank hold"
   rig humanoid
   pose start = plank
 
-  step "Brace" 3s ease-in-out:
-    spine: hold neutral
-    hips: hold neutral
+  step "Brace" 0.5s ease-in-out:
+    shoulders: flex 90
+    elbows: flex 90
+    elbows: pronate 80
     ground-lock: hands, feet
-    cue "Brace the core: one straight line from head to heels"
+    cue "Lower onto the forearms, elbows directly under the shoulders"
 
   step "Hold" 3s linear:
-    spine: hold neutral
+    shoulders: flex 90
+    elbows: flex 90
+    elbows: pronate 80
     ground-lock: hands, feet
-    cue "Keep breathing, ribs down, glutes engaged"
+    cue "Brace the core: one straight line from head to heels"
 
   repeat 3