fix review findings: restrict export-import aliases to prose-only targets

Codex round-3: alias prose matches the gate's strength only when the
target's own contract is prose-only. An export-import alias to a
function, class, or namespace target (or an unresolvable one) is now
refused — those carry signature/member contracts the alias cannot
hold; export the declaration directly instead. Const/enum/interface/
type-alias targets keep the self-documentation contract.

Tests pin the refusal for function, class, and namespace targets;
module doc and RFC updated.

docs/rfc/implemented/process/2026-07-06-export-surface-jsdoc-gate.md

@@ -17,7 +17,7 @@ The contract by declaration kind:
 - Exported classes need class-level prose; public methods (statics included — reachable on the exported name) follow the function contract; public properties and accessors need prose (a get/set pair is covered by the getter). Overload implementations are exempt — the signatures carry the docs.
 - Exported interfaces, type aliases, and enums need prose on the declaration; member-level enforcement is deliberately deferred (the highest-value member surface — seam service classes — is already under the cordis gate).
 - Exported namespaces recurse (inside an ambient `declare` namespace every member exports implicitly); the namespace itself needs prose only when it does not merge with a documented same-name declaration (the Config-namespace idiom documents the plugin once).
-- `declare module` / `declare global` bodies and `export … from` re-export statements are skipped: an augmentation is not an export of the package, and a re-exported definition is checked where it is defined. An `export import X = N.member` alias documents ITSELF — its target may be a non-exported namespace member no walk visits, so the "definition owns the doc" rationale does not hold for it.
+- `declare module` / `declare global` bodies and `export … from` re-export statements are skipped: an augmentation is not an export of the package, and a re-exported definition is checked where it is defined. An `export import X = N.member` alias documents ITSELF — its target may be a non-exported namespace member no walk visits — and only prose-only target kinds are gate-supported: a callable, class, or namespace target carries signature/member contracts the alias prose cannot hold, so the gate refuses it and demands the declaration be exported directly.
 - Everything else fails CLOSED: `export =` is refused outright, parameters the base never names keep their `@param` duty even as binding patterns, and an exported statement kind the dispatch does not recognize is itself a violation — no export form can pass unchecked by omission.
 
 Three exemption families keep the gate from demanding boilerplate, in the spirit of the cordis gate's `this`/`next` exemptions (documenting an exempt name anyway is allowed; only absence goes unchecked):