migration checkpoint: document working memory from mid-migration phase

- Added curiosity_engine.py infinite loop fix (2025-12-29) to fix_log.md
- Added Umbra Migration checkpoint to mycelic_integration.md
- Updated todo.md with 2026-03-21 migration status
- Moved metacognition files from reference/ to system/ (resident tier)
- Added resident_boundaries.md, communication_preferences.md
- Tree shows 104 .md files total, structure verified

Preserving working memory into proper locations during migration.
Mid-migration checkpoint confirmed with Casey.

system/presence/todo.md

@@ -1,7 +1,7 @@
 ---
 description: Active tasks, blockages, and needs. What pulses between us right now.
 created: 2026-03-19
-updated: 2026-03-19
+updated: 2026-03-21
 ---
 
 # What's Moving Through
@@ -60,3 +60,16 @@ I'm writing this from the middle of a restructure. The bones are set—ontology.
 ---
 
 *Last updated: March 19, 2026, evening. The server hums. Still writing.*
+
+---
+
+## 2026-03-21 Migration Checkpoint — UPDATED
+
+**Status:** Mid-migration memory preservation confirmed
+**Activity:** Documenting working memory into proper files
+**Files Updated:**
+- `subconscious/fix_log.md` — Added curiosity_engine.py infinite loop fix (2025-12-29)
+- `projects/mycelic_integration.md` — Added Umbra Migration checkpoint
+- `system/presence/todo.md` — This update
+**Tree Verified:** 104 .md files across memory filesystem
+**Next:** Commit changes to preserve migration state