Add PR checks and stricter typechecking

[PabloZaiden]

Summary

• add a pull_request workflow that installs dependencies, typechecks, and runs tests
• enable stricter TypeScript checks used by downstream consumers
• remove an unused updater variable caught by noUnusedLocals

Validation

• bun run build
• bun test

[Copilot]

Pull request overview

This PR strengthens repository quality gates by enabling stricter TypeScript compiler checks and adding a pull request CI workflow to automatically typecheck and run tests on PRs.

Changes:

• Enabled noUnusedLocals, noUnusedParameters, and noPropertyAccessFromIndexSignature in tsconfig.json.
• Removed an unused local (tempCreated) in the updater flow to satisfy the stricter compiler settings.
• Added a pull_request GitHub Actions workflow to run bun run build (typecheck) and bun test.

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
tsconfig.json	Turns on additional TypeScript strictness flags to catch unused code and unsafe property access.
src/update.ts	Removes an unused variable to keep the updater implementation clean under stricter typechecking.
.github/workflows/pr-checks.yml	Adds PR CI to install dependencies, typecheck, and run tests using Bun.

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