test: add bot fingerprint cases for common crawlers and CLI tools

## Summary
Expand `test/bot/fingerprint.test.ts` with realistic user-agent fixtures.

## Tasks
Add table-driven tests (or individual `it` blocks) for:
- `Googlebot`, `bingbot` → low score
- `curl`, `python-requests`, `scrapy` → elevated score
- Empty/missing `user-agent` → suspicious signals

Use `Request` + headers only — no network calls.

## Skills needed
Vitest, basic HTTP headers.

## Acceptance criteria
- [ ] At least 6 new user-agent scenarios
- [ ] `npm test` green

Start in test/bot/fingerprint.test.ts and review the existing fingerprint test patterns. Add at least six Request-and-headers-only scenarios covering the listed crawler, CLI, and empty or missing user-agent cases, then run npm test. Done means all scenarios are covered and the test suite is green.

Written by the indexing model from the issue text.