Add get_version_info tool — fleet identity attestation (v0.2.1)

[KI7MT]

Summary

Implements the fleet rollout per IONIS-AI/ionis-devel#49. solar-mcp is the exemplar — same diff shape fans out to the other 9 public servers next.

The new tool returns a standardized envelope:

{
  "service_name":    "solar-mcp",
  "service_version": "0.2.1",
  "spec_version":    "noaa-swpc-v1"
}

This is the minimum-viable identity attestation at the tool layer — agents can now confirm fleet alignment with a single call per server, without going outside the MCP protocol.

Why

Surfaced 2026-05-15 when Patton hit divergent values from solar:solar_conditions between Newton (9975WX) and Claude Desktop (M3). With no in-protocol way to ask "what version are you?", agents can't attribute divergence to version drift vs live-data timing vs config delta. get_version_info closes that gap fleet-wide.

Changes

• src/solar_mcp/__init__.py — add __spec_version__ Final constant, modernize to mirror the adif-mcp pattern
• src/solar_mcp/server.py — add get_version_info tool + _version_info_payload helper for direct test access without FastMCP wrapping
• tests/test_tools.py — TestGetVersionInfo class with 5 unit tests (SOLAR-L2-041 .. SOLAR-L2-045)
• README.md — tool added to the tools table
• CHANGELOG.md — new file, Keep a Changelog format
• pyproject.toml — version bump 0.2.0 → 0.2.1

Test plan

• L2 unit: 42 tests pass locally (pytest tests/test_tools.py)
• Security: 6 tests pass locally (pytest tests/test_security.py)
• CI matrix green
• Patton review (pattern lock before fan-out)

Convention reference

Locks the pattern for the remaining 9 public MCPs:

• pota, wspr, ionis, sota, iota, eqsl, qrz, lotw, hamqth

Plus inbox-mcp (private) and n1mm-mcp.