Remove legacy Remix export aliases

[brophdawg11]

Remix currently exposes package-aligned aliases alongside the canonical remix/* entrypoints. These compatibility mappings should not become part of the stable v3 API surface.

• Remove the 23 duplicate legacy mappings from the Remix manifest while retaining the canonical entrypoints.
• Preserve generated source stubs when a removed alias and a remaining canonical export share the same file.
• Add regression coverage that every generated Remix package export references an existing source file.
• Document each removed alias and its canonical replacement in the release note.

Generated packages/remix/package.json changes are intentionally left to the generate-remix CI workflow.

[github-actions]

Preview Build Available

A preview build has been created for this PR. You can install it using:

pnpm install "remix-run/remix#preview/pr-11599&path:packages/remix"

This preview build will be updated automatically as you push new commits.

[remix-run-bot]

Changes in this PR resulted in updates to the auto-generated remix package in 3d75ba3. Please review those changes prior to merging.