fix(pagination): reject fractional pagination flags

[JerryNee]

What

--page-size and --max-items are documented as integer pagination values, but shared pagination validation accepted fractional numbers like 1.5 and 2.5.

Why

Fractional pagination parameters are invalid per CLI docs/error wording and can produce surprising API requests. Local validation should reject them before credentials or network work.

Changes

• Require Number.isInteger for pageSize and maxItems.
• Add regression tests for fractional pageSize and maxItems.

Verification

• npx vitest run src/lib/pagination.test.ts src/commands/project.test.ts src/commands/test.test.ts
• npm run typecheck
• npm run lint
• npm run format:check
• npm test
• npm run build