refactor(navigation): unify use-case I/O schemas + presenter + feature error map

Per Plan 9 (spec R1-R28):
- getHeader use case: input z.object({}).strict() (R5); output =
  headerSchema parsed at runtime.
- getHeader controller: unknown input + identity presenter.
- New integrations/api/procedures.ts with navigationProcedure
  ([InputParseError → BAD_REQUEST], [HeaderNotFoundError → NOT_FOUND]).
- Router uses navigationProcedure + .input(getHeaderInputSchema).
- src/index.ts: remove headerQuery; export schemas + IUseCase/Controller
  aliases.
- src/ui/index.ts (NEW); package.json adds ./ui subpath.
- R25 + R26 tests added.

Refactor log: §1, §2, §3.1, §3.2, §3.3, §5.1, §5.2, §6.1, §6.2
Spec: R1–R6, R8–R15, R18–R20, R22–R26

packages/navigation/src/index.ts

@@ -1,3 +1,16 @@
 export type { Header, HeaderItem } from "./entities/models/header";
 export type { NavigationRouter } from "./integrations/api/router";
-export { headerQuery } from "./ui/query";
+export { HeaderNotFoundError } from "./entities/errors/header";
+export { InputParseError } from "./entities/errors/common";
+
+// Use case schemas + types (Plan 9 R18)
+export {
+  getHeaderInputSchema,
+  getHeaderOutputSchema,
+  type GetHeaderInput,
+  type GetHeaderOutput,
+  type IGetHeaderUseCase,
+} from "./application/use-cases/get-header.use-case";
+
+// Controller type aliases
+export type { IGetHeaderController } from "./interface-adapters/controllers/get-header.controller";