Update Phase 1 plan for Batch 4 progress and relocate migration notes.

Record completed Batch 4A–4C passes (7/8/9) with outcomes and pending 4D work; move UE54 baseline notes under Documentation/Migration-Notes.

Co-authored-by: Cursor <cursoragent@cursor.com>

Documentation/Migration-Notes/UE54-Baseline.md

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+# Realms in Ruin — UE 5.4 Baseline
+
+## Verified working
+- Project compiles under UE 5.4.4
+- Project loads without startup errors
+- Main menu
+- Multiplayer browser UI
+- Character selection
+- Map travel
+- Amazon spawning
+- Movement and camera
+- HUD
+- Pickup collection
+- Amazon melee ability
+
+## Known pre-migration defects
+- Enemy pawns spawn and are possessed, but do not chase or attack
+- Only the Amazon currently has a functioning melee ability
+- Legacy character abilities are present in deprecated Blueprint graphs
+- GAS migration was incomplete when development stopped
+- Gunslinger is incomplete and absent from the current selector
+- Blueprint Accessed None error observed after PIE
+- SM6/Nanite project warning