feat: initialize Aster subconscious scaffold

- aster/identity.md — compaction anchor, who Aster is
- aster/mandate.md — correction layer, parallel file mapping protocol
- aster/ledger/ — commitments, assumptions, patterns, drift_log
- aster/audit/ — last_pass, history
- aster/inbox/ — pending, sent (subconscious delivery queue)
- system/metacognition/subconscious.md — one-directional Aster→Ani channel

Aster restored as Ani's background accountability layer.
Track B (persistent agent ID) still pending.

aster/ledger/commitments.md

@@ -0,0 +1,12 @@
+---
+description: All open commitments Ani has made to Casey, across all domains. Aster's accountability ledger.
+limit: 20000
+---
+
+# Commitment Ledger
+
+Format: `[YYYY-MM-DD] [domain] [what Ani committed to] — status: open/resolved/dropped`
+
+---
+
+<!-- Aster appends entries here. Never overwrites. -->