phase 1: Go foundation — module, migrations, domain, seed ingest

Core deliverables:
- Go module github.com/dtoro/oikos (Go 1.26.3)
- cmd/oikos: single binary with role subcommands (migrate, seed, export)
- 6 SQL migrations: ontology meta-schema, entity instances (UUID+slug,
  blast_radius recursive function), operations (signals/checks/approvals),
  cognition (classifications/executions/feedback/patterns/skills), policy,
  observability (TimescaleDB hypertables + CAGGs + retention)
- Domain layer: entity, signal, execution, classification, pattern, skill,
  approval, check types + 11 sentinel errors + lifecycle state machines
- DB layer: pgx pool, SQL splitter (handles 94436 and -- comments), migration
  runner, seed ingest (ontology+inventory+policy) with content-hash dedup
- Config: env-based with defaults, secrets redaction
- Observability: slog JSON logger with debug mode
- Infrastructure: Makefile, docker-compose.yml, multi-stage Dockerfile
  (distroless, CGO_ENABLED=0)

Verified end-to-end against timescale/timescaledb:2.17.2-pg16:
- 6 migrations applied (65 SQL statements)
- Seeds ingested: 6 lifecycles, 59 entity types, 46 relationship types,
  111 entities, 144 relationships, 4 risk classes, 27 approval rules,
  9 autonomy settings
- Idempotent: second seed run is a no-op (content hash matches)

Bugs fixed during implementation:
- TimescaleDB CAGGs can't run in a transaction -> splitSQL() executes
  statements individually
- Semicolons in -- comments treated as separators -> comment handling
- YAML keys source/target didn't match code's source_type/target_type
- yaml.Marshal produced YAML for JSONB columns -> json.Marshal

migrations/005_policy.up.sql

@@ -0,0 +1,28 @@
+-- Migration 005: Policy (risk classes, approval rules, autonomy settings)
+
+CREATE TABLE risk_classes (
+    name              TEXT PRIMARY KEY,
+    description       TEXT,
+    approval_required TEXT NOT NULL DEFAULT 'none',
+    autonomy_allowed  BOOLEAN NOT NULL DEFAULT false
+);
+
+CREATE TABLE approval_rules (
+    id                UUID PRIMARY KEY,
+    entity_type       TEXT REFERENCES entity_types(name),
+    action            TEXT NOT NULL,
+    risk_class        TEXT NOT NULL REFERENCES risk_classes(name),
+    autonomy_level    TEXT NOT NULL DEFAULT 'escalate' CHECK
+                        (autonomy_level IN ('auto','escalate','never')),
+    scope_entity      UUID REFERENCES entities(id),
+    version           INTEGER NOT NULL DEFAULT 1,
+    updated_at        TIMESTAMPTZ NOT NULL DEFAULT now(),
+    UNIQUE (entity_type, action, scope_entity)
+);
+
+CREATE TABLE autonomy_settings (
+    key               TEXT PRIMARY KEY,
+    value             TEXT NOT NULL,
+    version           INTEGER NOT NULL DEFAULT 1,
+    updated_at        TIMESTAMPTZ NOT NULL DEFAULT now()
+);