Make MCP server name and title configurable

[Anika-Sol]

Summary

This PR makes the MCP server's name and title configurable during server start. The values can be set via flags (server-name and server-title) or environment variables (GITHUB_SERVER_NAME and GITHUB_SERVER_TITLE).

Why

Fixes #2158

What changed

• add the flags server-name and server-title with defaults resembling the previous hard coded name and title
• use the values of those flags when creating the MCP Server
• update documentation including an example

MCP impact

• No tool or API changes
• Tool schema or behavior changed
• New tool added

Security / limits

• No security or limits impact
• Auth / permissions considered
• Data exposure, filtering, or token/size limits considered

Tool renaming

• I am renaming tools as part of this PR (e.g. a part of a consolidation effort)
  • I have added the new tool aliases in deprecated_tool_aliases.go
• I am not renaming tools as part of this PR

Note: if you're renaming tools, you must add the tool aliases. For more information on how to do so, please refer to the official docs.

Lint & tests

• Linted locally with ./script/lint
• Tested locally with ./script/test

Docs

• Not needed
• Updated (README / docs / examples)