feat: Phase 2 — ports package, secrets port move, postgres adapter move

Problem: the hexagon's Phase 2 (plans/2026-08-15-hexagonal-architecture.md)
must give the use-cases-to-be their contract surface: driven-port
interfaces, test fakes, the secrets interface moved into core, and the
postgres package inside the adapters tree — before the first vertical
slice (Phase 3) can wire a composition root.

Change:
- internal/core/ports: full driven-port catalog per plan §3.3 —
  repositories as transaction-scoped aggregates whose inputs carry
  derived checks, audit, and events (§3.6), plus CommandExecutor,
  TargetResolver, Checker, Secrets, EventPublisher, Provisioner.
  Port-local payload types (Event, AuditEntry, CheckDef, KnowledgeEntry,
  ExecResult) keep signatures off infrastructure; TypeTree aliases
  internal/ontology (pure over domain) until checkdefaults is absorbed.
  ReadModels intentionally not declared yet — it materializes with the
  Phase 3 slice and grows as report handlers rewire.
- secrets.Backend is now an alias of ports.Secrets; implementations
  (Infisical, SOPS, Manager) unchanged. mcp's local secretBackend
  subset is deleted; tool constructors take ports.Secrets.
- internal/db → internal/adapters/postgres (mechanical import rewrite;
  package identifier stays db until the Phase 3 repository split).
  sqlc.yaml, Makefile, golangci exclusions, and docs follow the move;
  make generate-check verified.
- internal/adapters/ssh: Executor implements ports.CommandExecutor over
  the actuator dial pool + RunStreaming (10-min default timeout carried
  over from the httpapi path).
- internal/adapters/remote: Resolver implements ports.TargetResolver
  delegating to internal/remote (still pool-based; drops onto
  ports.EntityRepository when repositories land in Phase 3 — documented
  transitional import).
- internal/core/ports/portstest: importable fakes — in-memory
  EntityRepo (with check-then-act SetState, side-effect recording),
  RecordingExecutor, FakeChecker, SpyPublisher; port-satisfaction
  guards; tests.

Risk: ports are declared ahead of implementations — signatures firm up
per phase as slices land (documented in the package doc); the
remote→postgres transitional import is explicit and dissolves in
Phase 3.

Verification: go vet, make test (race, 19 packages), generate-check,
golangci on core+adapters — 0 issues; full-repo baseline down
365→344.

internal/core/ports/entities.go

@@ -0,0 +1,83 @@
+package ports
+
+import (
+	"context"
+
+	"github.com/dtoro/oikos/internal/core/domain"
+	"github.com/dtoro/oikos/internal/ontology"
+)
+
+// TypeTree aliases the ontology tree: entity types, relationship types,
+// lifecycle definitions. ontology is pure over domain; it moves under
+// core/ when checkdefaults is absorbed (Phase 3).
+type TypeTree = ontology.TypeTree
+
+// EntityFilters bounds entity list/search reads.
+type EntityFilters struct {
+	Type  string
+	State string
+	Q     string
+	Limit int
+}
+
+// EntityCreateInput is one transaction: the entity, its derived check
+// definitions, and the audit/event side-effects of the creation.
+type EntityCreateInput struct {
+	Entity        domain.Entity
+	DerivedChecks []CheckDef
+	Audit         []AuditEntry
+	Event         *Event
+}
+
+// EntityUpdateInput mirrors EntityCreateInput for updates.
+type EntityUpdateInput struct {
+	Entity        domain.Entity
+	DerivedChecks []CheckDef
+	Audit         []AuditEntry
+	Event         *Event
+}
+
+// EntityTransitionInput is a lifecycle state change: the check-then-act
+// precondition (current state) is validated inside the transaction.
+type EntityTransitionInput struct {
+	Slug         string
+	From         string
+	To           string
+	Audit        []AuditEntry
+	Event        *Event
+}
+
+// EntityRepository is the entity aggregate. Command methods are
+// transaction-scoped: everything in the input commits or nothing does.
+type EntityRepository interface {
+	Get(ctx context.Context, id domain.UUID) (domain.Entity, error)
+	BySlug(ctx context.Context, slug string) (domain.Entity, error)
+	List(ctx context.Context, filters EntityFilters) ([]domain.Entity, error)
+	Search(ctx context.Context, q string, limit int) ([]domain.Entity, error)
+
+	Create(ctx context.Context, input EntityCreateInput) (domain.Entity, error)
+	Update(ctx context.Context, input EntityUpdateInput) (domain.Entity, error)
+	SetState(ctx context.Context, input EntityTransitionInput) (domain.Entity, error)
+}
+
+// RelationshipCreateInput validates endpoints against the ontology in core
+// before this is called; the repository persists the edge (+audit/event).
+type RelationshipCreateInput struct {
+	Relationship domain.Relationship
+	Audit        []AuditEntry
+	Event        *Event
+}
+
+// RelationshipRepository is the relationship aggregate.
+type RelationshipRepository interface {
+	Create(ctx context.Context, input RelationshipCreateInput) (domain.Relationship, error)
+	End(ctx context.Context, source, target domain.UUID, relType string) error
+	ListFor(ctx context.Context, entityID domain.UUID, direction string) ([]domain.Relationship, error)
+}
+
+// OntologyStore loads the type tree; implementations cache. Consumers
+// validate entity types, relationship endpoints, and lifecycle transitions
+// against it before issuing repository writes.
+type OntologyStore interface {
+	LoadTypeTree(ctx context.Context) (TypeTree, error)
+}