feat(mcp): parse mcp tool json

[burmudar]

Define structures to parse the mcp tool json

• define general Schema which can be used for Input and Out schema definitions
• define SchemaValue interface to unitfy types under one umbrella
• specilzied schema types: SchemaObject, SchemaArray, SchemaPrimitve
• special handling for when items: true

Part of SRCH-2167

Test plan

Added testcase and parsed the dumped json

[burmudar]

This change is part of the following stack:

• feat(mcp): add script to dump mcp tool list #1211
  • feat(mcp): parse mcp tool json #1212 ◀
    • feat(mcp): add mcp list-tools to list available tool calls #1213
      • feat(mcp): build flagset from mcp input schema to parse args #1215
        • feat(mcp): do mcp tool call from cli args #1216

_{Change managed by git-spice.}

[burmudar]

temporarily ignored

[keegancsmith]

minor: you might as well only define the fields on these structs you will actually end up reading.

And my favourite nit: probably not used outside of this package so don't export.

[keegancsmith]

minor: is there any chance the tool order matters? I think in the backend we also use a map and just sort by name when serializing for determinism, but I can't remember.

[keegancsmith]

can't we remove SchemaValue and just use a normal go interface? Then we just have some sort of standard set of go types we could marshal into (same as how the json library works in go)

[keegancsmith]

a nicer test here would probably just load in mcp_tools.json and then assert on some stable tool's properties. eg the read file tool likely won't change.