chore(tests): re-register def-pre-position-mobile-reserve in UPGRADED

The pack YAML was un-registered from UPGRADED (commit 5fd7e8d) when a
sibling agent observed the entry was orphaned (no YAML in git). With
the YAML now committed (8879e4b), re-add the entry so the hard-tier
spawn-variation invariant covers the pack.

tests/test_hard_tier.py

@@ -217,10 +217,19 @@ UPGRADED = [
     # (enemy actors don't honour spawn_point — CLAUDE.md) so a memorised
     # base layout cannot generalise.
     "lh-defense-tech-second-base",
-    # NOTE: "def-pre-position-mobile-reserve" — Wave-5 agent crashed
-    # before its YAML hit git; the entry below was registered by a
-    # sibling agent who saw the in-flight worktree. Removed from
-    # UPGRADED until a re-spawn agent produces the pack.
+    # Wave-5 Group C reasoning pack — central mobile reserve doctrine
+    # / chess-piece centralization / military QRF. Hard tier defines
+    # two agent spawn_point groups (centre column x=40 / x=50)
+    # round-robined by seed so the reserve's exact staging cell varies
+    # but both remain equidistant from N/S flanks; THREE simultaneous
+    # rush bands (N/S/E) always place (enemy actors don't honour
+    # spawn_point — CLAUDE.md), so a single committed-flank policy
+    # cannot generalise. The forward-zone clause (`all_of` THREE
+    # `units_in_region_gte`) is the load-bearing discriminator: a
+    # passive central reserve auto-engages but never satisfies the
+    # forward zones; only an active three-way split / staggered send
+    # wins.
+    "def-pre-position-mobile-reserve",
     # Wave-5 Group C reasoning pack — ERQA spatial commit / MicroRTS
     # terrain-aware defence / military pre-positioned defence /
     # intel-driven facility hardening anchor. The model is TOLD where