Migrate test-app to vite (ember.nvp-style), scenario-test via @embroider/try, drop TS 5.9

[NullVoxPopuli-ai-agent]

Follows up on #15. Everything verified locally: full workspace turbo build lint test typecheck green; default suite 163 pass / 1 skip / 0 fail; ember-lts-5.12 (compat) and ember-lts-6.4 (pure vite) scenarios run green end-to-end locally.

test-app → vite

Modeled on pnpm dlx ember.nvp output (qunit + typescript + inspector-support layers):

• @nullvoxpopuli/ember-vite + (rolldown-)vite 8, ember-source 7, @glimmer/component 2, glint 2 (ember-tsc), testem running the built dist.
• Strict application resolver with an import.meta.glob modules map; the ember-data store service is registered explicitly (app/services/store.ts) since there's no app-tree merging.
• Route templates converted from loose .hbs to gts route components typed as TOC<{ Args: { controller; model } }>; ember-page-title dropped; ember-sinon-qunit replaced by a QUnit.testDone(() => sinon.restore()).
• All the ember-cli/broccoli machinery is gone (ember-cli, auto-import, webpack, ember-template-imports, resolver, load-initializers, config/environment, …).
• The hbs/classic-reexport smoke test was removed — it specifically exercised loose-mode app-tree resolution, which has no strict-mode equivalent. The _app_ re-exports themselves still ship and are exercised by the 5.x compat scenarios' builds.

Matrix testing → @embroider/try (per ember-cli/ember-addon-blueprint)

• Scenarios live in test-app/.try.mjs; the Default Tests job emits the matrix via @embroider/try list, and the try job does apply → pnpm install --no-lockfile → pnpm turbo test (with ENABLE_COMPAT_BUILD in turbo's env inputs).
• ember-lts-5.8 / ember-lts-5.12 swap in @embroider/compat's classic build (own vite/babel configs, ember-cli-build.cjs — which is also where macros own-config must live in compat mode) pinned to vite 7. ember-lts-6.4, latest, beta, alpha run pure vite 8.
• The a11y acceptance tests (the only route-visiting tests) are gated on ember-source >= 6.3, where component route templates landed; 5.x scenarios still run all 160 rendering/unit tests.
• Support-floor note: the previous ember-try matrix nominally covered 4.4/4.8, but hadn't actually passed in a very long time. The vite/compat harness bottoms out at 5.8. Peer ranges (ember-source >=4.4.0) are unchanged — older versions are simply no longer CI-verified. Happy to bump the floor in a follow-up if you'd rather the peers tell the truth.

Package changes surfaced by pure-vite consumption

• ember-async-data ^2 and tracked-built-ins ^4 (their old versions dragged in v1-addon transitives — @ember/test-waiters@3, ember-tracked-storage-polyfill — which can't load outside a classic build).
• Dropped the @glimmer/tracking peer: at runtime that module has always come from ember-source (the npm package is types-only and lacks cached); the real package shadowing ember-source's copy breaks vite builds.
• Peers widened: @glimmer/component ^1.1.2 || ^2.0.0, ember-changeset ^4.1.2 || ^5.0.0.
• Removed "./-private/*": null from the exports map — embroider-vite resolves the dist's relative -private imports through the exports map, so the null entry breaks consumers.
• test-app: ember-changeset 5 and ember-a11y-testing 8 (both v2 addons), explicit axe-core.

CI

• TS matrix drops typescript@5.9, keeping 6.0.
• try-scenarios job rewritten for the dynamic @embroider/try matrix (fail-fast off, per-scenario env).
• pnpm-workspace.yaml allows esbuild builds (vite 7 in compat scenarios).

Not touched

• docs-app stays on its classic webpack build for now (docfy/oss-docs are a separate migration).
• Runtime source of the addon packages is unchanged — everything above is dependency/metadata level.

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