Add Xquik MCP tool example

[kriptoburak]

What

Adds a FastMCP example tool for Xquik under mcp/xquik_tool.

The tool exposes read-only helpers for:

• public X post search
• public X user search
• public X trends

It follows the existing MCP example layout with a README, Dockerfile, pyproject, startup smoke script, and uv lockfile.

Why

Kagenti's MCP examples already include focused external data tools. This adds a public X research example that keeps authentication in XQUIK_API_KEY and uses source-confirmed Xquik REST routes.

Validation

• Confirmed kagenti/agent-examples is active and Apache-2.0 licensed.
• Checked all-state issues and PRs for existing Xquik entries.
• Checked the target default branch for existing Xquik references.
• Verified live Xquik OpenAPI routes and x-api-key auth.
• uvx ruff check mcp/xquik_tool/xquik_tool.py
• uvx ruff format --check mcp/xquik_tool/xquik_tool.py
• uv run --locked python -m py_compile xquik_tool.py
• Missing-key behavior check for all 3 tools.
• expect -f test_startup.exp
• Target pre-commit hooks on the changed files.
• Staged whitespace and confidentiality scans.

[pdettori]

Thank you @kriptoburak for your contribution- we appreciate his contribution demonstrating the extensibility of kagenti, but we think the current set of MCP tools is sufficient as-is