test: add library quality gates and package validation

[terminalchai]

Closes #80.

Adds explicit vue-tsc --noEmit checking and a smoke test that packs the library, installs the tarball in a temporary consumer, imports the public entry point, resolves every current public subpath, checks required tarball files including CSS, and typechecks a consumer import. The existing CI workflows now use npm ci, with typechecking, distribution validation, and package validation added to the build workflow.

The consumer test exposed missing Vue component declarations in the packed artifact. Explicitly selecting the Vue declaration processor and declaring its @vue/language-core peer makes those declarations available. Node types are also declared directly, and two existing render-task mocks now include the required promise so the new typecheck passes. Public exports and component behavior are unchanged; repository strict mode is unchanged.

Validation after a clean npm ci, using Node 24.20.0 and npm 11.19.1:

• Lint and typecheck pass.
• All 79 unit tests pass.
• Library build, distribution validation, and packed-package consumer test pass.
• Demo build passes.
• REUSE lint passes for all 53 files.

Vite still prints its existing advisory about future native config loading; all checks exit successfully.