fix(barrel-policy): skip export statements inside ambient module declarations

[Mearman]

Summary

• `export * from`/`export { x } from` written purely inside a `declare module "..." { ... }` (a TSModuleDeclaration) describes an external package's or namespace's types -- no real runtime import chain exists at that location
• barrel-policy was matching this syntax the same as a genuine re-export, flagging the routine pattern of typing an otherwise-untyped npm package by re-exporting another package's types under a declared module name (e.g. `declare module "untyped-pkg" { export * from "typed-pkg"; }`)
• New `isInsideAmbientModuleDeclaration` helper walks the parent chain generically (not asserting a specific parser's node types) and both `ExportNamedDeclaration`/`ExportAllDeclaration` handlers in barrel-policy now skip nodes inside one
• Confirmed live migrating a real consumer onto this package: a `.d.ts` ambient shim for an untyped plotting library was flagged as a barrel-policy violation; zero once this fix is applied

Test plan

• `pnpm lint` / `pnpm typecheck` / `pnpm test` (346/346, one clean full run plus a second confirming no flakiness) / `pnpm build` all green
• New valid-case tests: a re-export inside `declare module "pkg" { ... }` and inside `declare module Namespace { ... }`, both in the strictest (`banned`) mode

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
🔒 Security Review	✅ Completed 2026-09-03T04:45:59.478588Z	9cc56ea	PR opened

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[github-actions]

🎉 This PR is included in version 2.10.4 🎉

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