Add the remaining census stations: Pec Deck, Rear Delt Fly, cable staples

Pec Deck and Rear Delt Fly author the face-on and from-behind cameras;
Triceps Pushdown and Face Pull are the cable station's two entries per
the coverage model (cable curl/crossover are considered exclusions).

Claude-Session: https://claude.ai/code/session_01HJDQQDA9QdP8zByg43H5v3

Exercise Library/Pec Deck/info.md

@@ -0,0 +1,40 @@
+# Pec Deck
+
+The machine chest fly — arms sweep together in front of the chest along
+the machine's fixed arc.
+
+- **Category:** Main circuit
+- **Type:** Machine-based chest fly
+- **Targets:** Chest, front delts
+- **Prescription:** 4 × 10
+
+## Setup
+
+Adjust the seat so the handles sit at chest height with your upper arms
+level. Back flat on the pad, feet planted, a soft bend fixed in the
+elbows.
+
+## Execution
+
+1. Sweep both arms together in a wide arc until the handles meet in
+   front of the chest.
+2. Squeeze the chest hard for a beat at the middle.
+3. Open back up with control until you feel a full chest stretch.
+
+## Cues
+
+- Elbow angle never changes — the chest swings the arms.
+- Shoulders stay back against the pad; they don't roll forward at the
+  squeeze.
+- Slow the return; the stretch half of the rep counts.
+
+## Common Mistakes
+
+- Setting the seat so low the handles sit at the shoulders.
+- Shoulders rounding forward to chase extra range.
+- Letting the stack yank the arms open.
+
+## Progression
+
+Add a plate once every rep meets in the middle with a one-second
+squeeze; the Dumbbell Fly trades the guided path for free control.