Replace jest+puppeteer with mocha+jsdom in examples/apps

[alexvy86]

Summary

Migrates 9 packages in examples/apps/ from Jest+Puppeteer (browser E2E tests) to Mocha+jsdom (unit/component tests), following the same pattern used by examples/data-objects/inventory-app/ and packages/framework/react/.

Packages changed:

• blobs, collaborative-textarea, contact-collection, data-object-grid, diceroller, presence-tracker, staging, task-selection, tree-comparison

Per-package changes:

• Deleted jest.config.cjs, jest-puppeteer.config.cjs, and tests/ directories (old Puppeteer E2E tests)
• Added .mocharc.cjs using @fluid-internal/mocha-test-setup
• Added src/test/tsconfig.json extending tsconfig.test.node16.json
• Updated package.json: swapped Jest/Puppeteer devDeps for mocha, @types/mocha, global-jsdom, jsdom, @fluid-internal/mocha-test-setup; added build:test:esm/test:mocha/test:mocha:esm scripts
• Updated tsconfig.json: removed Jest types, added rootDir: "./src", excluded src/test/**
• Added new unit/component tests under src/test/ that test React components via @testing-library/react and data model logic directly

Test plan

• pnpm build from repo root passes (all 1461 tasks)
• pnpm test:mocha:esm passes in all 9 packages (29 tests total)
• ESLint passes in all 9 packages

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