Add Phase 1 experimenter tools: MCP server, H21cm, beacon logger, arc survey

Four new tools transforming the SkyWalker-1 from satellite TV receiver into
a general-purpose RF observatory:

- skywalker-mcp: FastMCP server exposing 20 tools, 4 resources, 2 prompts.
  Thread-safe DeviceBridge with motor safety (continuous drive opt-in),
  input validation on all frequency/symbol rate/step parameters,
  try/finally on TS capture, path traversal sanitization, and reduced
  lock scope so emergency motor halt isn't blocked during long surveys.

- h21cm.py: Hydrogen 21 cm drift-scan radiometer at 1420.405 MHz with
  Doppler velocity calculation, control band comparison, and CSV output.

- beacon_logger.py: Long-term Ku-band beacon SNR/AGC logger with auto-relock,
  dual CSV/JSONL output, signal handlers, and systemd unit generation.

- arc_survey.py: Multi-satellite orbital arc census with USALS motor control,
  per-slot catalog persistence, resume support, and defensive motor halt
  on all error/interrupt paths.

Documentation: experimenter's roadmap guide + 4 tool reference pages (48 pages total).

mcp/skywalker-mcp/pyproject.toml

@@ -0,0 +1,35 @@
+[build-system]
+requires = ["hatchling"]
+build-backend = "hatchling.build"
+
+[project]
+name = "skywalker-mcp"
+version = "2026.2.17"
+description = "MCP server for the Genpix SkyWalker-1 DVB-S USB receiver"
+requires-python = ">=3.11"
+authors = [{name = "Ryan Malloy", email = "ryan@supported.systems"}]
+dependencies = [
+    "fastmcp>=2.0",
+    "pyusb>=1.3",
+]
+
+[project.scripts]
+skywalker-mcp = "skywalker_mcp.server:main"
+
+[tool.hatch.build.targets.wheel]
+packages = ["src/skywalker_mcp"]
+
+[project.optional-dependencies]
+dev = [
+    "pytest>=8.0",
+    "pytest-asyncio>=0.24",
+    "ruff>=0.9",
+]
+
+[tool.ruff]
+target-version = "py311"
+line-length = 100
+
+[tool.pytest.ini_options]
+testpaths = ["tests"]
+asyncio_mode = "auto"