feat: structured output support (MCP 2025-06-18 spec)

[Sbussiso]

Summary

Enable smolagents structured_output=True support so the agent sees tool output schemas upfront, reducing wasted steps and silencing the FutureWarning.

Tools now return Pydantic model instances (not json.dumps strings) when response_format="json", so FastMCP emits outputSchema and structuredContent per the MCP 2025-06-18 spec.

Changes

• New Pydantic output models for all 14 tools across 3 modules:
  • Thingiverse: SearchResult, SearchResultItem, ModelDetails, ModelFile, DownloadResult, DownloadedFile, SkippedFile
  • Cura: SliceResult, SliceSettings, SliceStats
  • OctoPrint: StatusResult, ServerInfo, ConnectionInfo, TemperatureReading, FileListResult, FileEntry, JobResult, ConnectResult, UploadResult, StartPrintResult, ControlJobResult, TemperatureResult, HomeResult, MoveResult, DryRunPreview
• Refactored tools to return model instances on the JSON path; markdown path unchanged (still returns str)
• Dry-run paths (confirm=false) on actuation tools now return a DryRunPreview model on the JSON path — the tool always returns the declared type regardless of the confirm flag
• Return type annotations updated from -> str to -> str | <ResultModel> (or -> str | DryRunPreview | <ResultModel> for actuation tools)
• Tests updated to assert Pydantic instances on the JSON path and str on the markdown path. New tests verify all 14 tools emit outputSchema and that model schemas match.
• Version bump 0.1.1 → 0.2.0

Backward Compatibility

• The response_format="markdown" path (the default) is unchanged — still returns a human-readable str.
• Error strings ("Error: ...") are still returned as str on all paths.
• The JSON payload shape is identical to before — only the type of the returned Python object changed (model instance instead of JSON string). On the MCP wire, structuredContent carries the same fields.

Reference

• smolagents structured output docs
• MCP 2025-06-18 spec update

Consumer

PrintPal/main.py will pass structured_output=True to MCPClient after this lands.

Test Plan

• uv run pytest -q — 83 passed
• uvx ruff check src tests — all checks passed
• uvx ruff format --check src tests — 10 files already formatted
• uv build && uvx twine check dist/* — both PASSED
• End-to-end verification: all 14 tools emit outputSchema