chore: initialize overstory and ecosystem tools

.mulch/README.md

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+# .mulch/
+
+This directory is managed by [mulch](https://github.com/jayminwest/mulch) — a structured expertise layer for coding agents.
+
+## Key Commands
+
+- `mulch init`      — Initialize a .mulch directory
+- `mulch add`       — Add a new domain
+- `mulch record`    — Record an expertise record
+- `mulch edit`      — Edit an existing record
+- `mulch query`     — Query expertise records
+- `mulch prime [domain]` — Output a priming prompt (optionally scoped to one domain)
+- `mulch search`   — Search records across domains
+- `mulch status`    — Show domain statistics
+- `mulch validate`  — Validate all records against the schema
+- `mulch prune`     — Remove expired records
+
+## Structure
+
+- `mulch.config.yaml` — Configuration file
+- `expertise/`        — JSONL files, one per domain