feat: add OOT (Out-of-Tree) block path loading support
Add load_oot_blocks MCP tool to dynamically load GNU Radio OOT modules.
Since GRC's Platform.build_library() clears all blocks on every call,
the implementation combines default block paths with OOT paths before
rebuilding. This allows loading custom blocks from:
- /usr/local/share/gnuradio/grc/blocks (locally-built)
- Custom user-specified directories
Implementation:
- PlatformMiddleware.load_oot_paths(): validates paths, combines with
defaults, rebuilds library
- PlatformProvider.load_oot_blocks(): exposes method to MCP layer
- McpPlatformProvider: registers load_oot_blocks tool
Returns useful diagnostics: added_paths, invalid_paths, and block
counts before/after reload.
Ryan Malloy
e9ac115728