feat: add --version flag and version introspection tool

[BryanFRD]

Package
Which package does this affect? [x] server [ ] tools [ ] docs

Problem / Motivation
There's no way for a consumer to ask the MCP server what version it's running.

Add a `--version` CLI flag and optionally a `get_version` MCP tool for runtime introspection. Useful for debugging version mismatches.

Proposed solution
To be defined — see Problem / Motivation above.

Alternatives considered
None considered explicitly — this is the natural shape.

Additional context
None.