Add the hinge pattern: Deadlift, RDL, Glute Bridge, Hip Thrust, Back Extension

The biggest hole in the coverage matrix - the hinge had zero entries in
any modality. Deadlift and Romanian Deadlift are the library's first
standing (camera.zoom) and first barbell motions.

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

Exercise Library/Glute Bridge/info.md

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+# Glute Bridge
+
+The floor hip hinge — drive through the heels and lift the hips until the
+body is a straight line from shoulders to knees.
+
+- **Category:** Warm-up and main circuit
+- **Type:** Hip extension (floor)
+- **Targets:** Glutes, hamstrings
+- **Prescription:** 3 × 12–15, squeeze at the top
+
+## Setup
+
+Lie on your back, knees bent, feet flat on the floor about hip-width and
+close enough that your fingertips can graze your heels. Arms rest at your
+sides.
+
+## Execution
+
+1. Press through the heels and squeeze the glutes to lift the hips.
+2. Stop when shoulders, hips and knees form a straight line — no arching
+   past it.
+3. Hold the squeeze for a beat, then lower with control.
+
+## Cues
+
+- The glutes lift the hips; the lower back just comes along.
+- Ribs stay down — finish with the glutes, not by overarching.
+- Knees track over the feet, never falling inward or out.
+
+## Common Mistakes
+
+- Pushing through the toes instead of the heels.
+- Overarching the lower back at the top.
+- Bouncing reps off the floor.
+
+## Progression
+
+Pause holds at the top, then single-leg bridges; graduate to the barbell
+Hip Thrust for load.