chore(e2e): remove legacy mock/real vLLM test modes and Makefile targets

[samzong]

What type of PR is this?

chore: remove legacy mock/real vLLM test modes and Makefile

What this PR does / why we need it:
Drop the --mock / --real flags from e2e-tests/run_all_tests.py and remove
legacy start/stop and test targets for mock/real vLLM servers from the
tools/make/build-run-test.mk. Simplifies the e2e workflow to rely on the
LLM Katan flow and the manual start/run pattern.

Which issue(s) this PR fixes:

Fixes #420

Release Notes: Yes

[netlify]

✅ Deploy Preview for vllm-semantic-router ready!

Name	Link
🔨 Latest commit	bccd2d0
🔍 Latest deploy log	https://app.netlify.com/projects/vllm-semantic-router/deploys/68ee0e3ad2ff670008ddbefd
😎 Deploy Preview	https://deploy-preview-421--vllm-semantic-router.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[github-actions]

👥 vLLM Semantic Team Notification

The following members have been identified for the changed files in this PR and have been automatically assigned:

📁 e2e-tests

Owners: @yossiovadia
Files changed:

• e2e-tests/run_all_tests.py

📁 tools

Owners: @yuluo-yx, @rootfs, @Xunzhuo
Files changed:

• tools/make/build-run-test.mk

---

🎉 Thanks for your contributions!

This comment was automatically generated based on the OWNER files in the repository.

[rootfs]

@yossiovadia PTAL, thanks

[Copilot]

Pull Request Overview

This PR removes legacy test infrastructure for mock and real vLLM server modes from the e2e testing workflow. The changes simplify the testing process by consolidating to use only the LLM Katan flow, which provides lightweight real model testing.

Key changes:

• Removed --mock and --real command-line flags from the test runner
• Eliminated legacy Makefile targets for starting/stopping mock and real vLLM servers
• Streamlined to a single manual workflow using LLM Katan servers

Reviewed Changes

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

File	Description
tools/make/build-run-test.mk	Removed legacy Makefile targets for mock/real vLLM server management and testing
e2e-tests/run_all_tests.py	Removed command-line arguments and mode detection logic for mock/real vLLM testing

---

_{Tip: Customize your code reviews with copilot-instructions.md. Create the file or learn how to get started.}