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.

.agents/dev/CONTRIBUTING.md

@@ -14,9 +14,9 @@ cmd/webhook/main.go        Gitea deploy-webhook receiver (push-to-deploy on mac-
 internal/httpapi/           REST + MCP server. Chi router. OpenAPI-generated types from
                              internal/httpapi/gen/api.gen.go. Strict server in impl.go.
 internal/mcp/               MCP tool implementations (get_entity, search_knowledge, etc.)
-internal/db/                Connection pool (pool.go), seed ingestion (seed.go), DB→YAML
+internal/adapters/postgres/  Connection pool (pool.go), seed ingestion (seed.go), DB→YAML
                              export (export.go), type hierarchy (typetree.go)
-internal/db/queries/        SQL query files → sqlc generates internal/db/sqlcgen/
+internal/adapters/postgres/queries/  SQL query files → sqlc generates sqlcgen/ (same dir)
 internal/scheduler/         Observe loop: probes, signals, check_defs
 internal/actuator/          SSH execution with circuit breaker + retry
 internal/learning/          Pattern extraction, anomaly detection
@@ -91,8 +91,8 @@ current phase status). To add a new capability:
 
 ## SQL conventions
 
-- Queries live in `internal/db/queries/*.sql` with `-- name: FuncName :exec`
-  annotations for sqlc. Generated code in `internal/db/sqlcgen/` — never
+- Queries live in `internal/adapters/postgres/queries/*.sql` with `-- name: FuncName :exec`
+  annotations for sqlc. Generated code in `internal/adapters/postgres/sqlcgen/` — never
   hand-edit. Call via `sqlcgen.New(pool).QueryName(ctx, params)`.
 - **sqlc is the default** for all DB access. Raw `pool.Query/Exec` with inline
   SQL is a documented carve-out for cases sqlc can't express: `LISTEN`/`NOTIFY`,