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/adapters/remote/resolver.go

@@ -0,0 +1,63 @@
+// Package remote implements ports.TargetResolver over internal/remote.
+// The resolver logic (address preference, guest wrapping, hosting-compute
+// walks) is unchanged; this adapter maps its results onto the port types.
+// When the postgres repositories land (Phase 3+), the underlying functions
+// move into this package on top of ports.EntityRepository.
+package remote
+
+import (
+	"context"
+
+	"github.com/google/uuid"
+
+	postgres "github.com/dtoro/oikos/internal/adapters/postgres"
+	"github.com/dtoro/oikos/internal/core/domain"
+	"github.com/dtoro/oikos/internal/core/ports"
+	intremote "github.com/dtoro/oikos/internal/remote"
+)
+
+// Resolver resolves execution targets from the entity graph.
+type Resolver struct {
+	pool *postgres.Pool
+}
+
+var _ ports.TargetResolver = (*Resolver)(nil)
+
+// NewResolver builds a resolver over the postgres pool.
+func NewResolver(pool *postgres.Pool) *Resolver { return &Resolver{pool: pool} }
+
+func toPort(t intremote.ExecTarget) ports.Target {
+	return ports.Target{Host: t.Host, User: t.User, Wrap: t.Wrap}
+}
+
+// ResolveExecTarget resolves a slug to its execution endpoint.
+func (r *Resolver) ResolveExecTarget(ctx context.Context, targetSlug string) (ports.Target, error) {
+	t, err := intremote.ResolveExecTarget(ctx, r.pool, targetSlug, intremote.DefaultUser)
+	if err != nil {
+		return ports.Target{}, err
+	}
+	return toPort(t), nil
+}
+
+// ResolveForCheck resolves a check's entity (by ID and type) to its endpoint.
+func (r *Resolver) ResolveForCheck(ctx context.Context, targetID domain.UUID, targetType string) (ports.Target, error) {
+	id, err := uuid.Parse(string(targetID))
+	if err != nil {
+		return ports.Target{}, err
+	}
+	t, err := intremote.ResolveExecTargetForCheck(ctx, r.pool, id, targetType, intremote.DefaultUser)
+	if err != nil {
+		return ports.Target{}, err
+	}
+	return toPort(t), nil
+}
+
+// ResolveHost resolves a host slug to address and SSH user.
+func (r *Resolver) ResolveHost(ctx context.Context, hostSlug, fallbackUser string) (string, string, error) {
+	return intremote.ResolveHost(ctx, r.pool, hostSlug, fallbackUser)
+}
+
+// IsGuest reports whether an entity type is reached via pct/qm exec.
+func (r *Resolver) IsGuest(entityType string) bool {
+	return intremote.IsGuest(entityType)
+}