Enable Glint by default for both JS and TS addons

[wagenet]

Summary

Implements RFC #976: Enable Glint by Default for the addon blueprint. Mirrors the app-blueprint change at ember-cli/ember-app-blueprint#273.

• Move `@glint/ember-tsc`, `@glint/template`, `@glint/tsserver-plugin`, and `typescript` out of the `<% if (typescript) %>` blocks in `package.json` — installed unconditionally so JS addons get IDE tooling. `@ember/app-tsconfig` and `@ember/library-tsconfig` were already always-installed. `lint:types` stays TS-only (`ember-tsc --noEmit`).
• Add `files/jsconfig.json` for the JS path; filter it out of TS addons in `index.js`.
• Drop dead loose-mode artifacts (Glint v2 supports template-tag only):
  • `files/src/template-registry.ts`
  • The `'template-registry.js'` rollup public entrypoint
  • Matching test snapshot assertions in `tests/smoke-tests/--typescript.test.ts` and `tests/rollup-build-tests/explicit-imports.test.ts`
  • The v1-registry fixture files at `tests/fixtures/explicit-imports/`

Related

• RFC: Enable Glint by Default emberjs/rfcs#976
• Companion app-blueprint PR: Enable Glint by default for both JS and TS apps ember-app-blueprint#273
• Companion change in upstream ember-cli (legacy blueprints): Switch app and addon blueprints to Glint v2 ember-cli#11015
• Docs: typescript: document Glint as a default ember-learn/guides-source#2211
• Announcement post: Add Glint-by-default announcement post ember-learn/ember-blog#1373

Test plan

• Generate a JS addon — confirm `jsconfig.json` present, no `tsconfig.json`, Glint v2 packages installed, no `lint:types` script.
• Generate a TS addon — confirm `tsconfig.json`, no `jsconfig.json`, only Glint v2 deps, `lint:types` runs `ember-tsc --noEmit`.
• CI: existing rollup-build and smoke tests pass with the updated snapshots.

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