Add a zero-training method to the methods/ framework (e.g. TSCG)

[Code-byte404]

Type: help wanted

Toolhound benchmarks existing zero-training tool-calling fixes; PA-Tool is integrated. Add another (e.g. TSCG, or a constrained-decoding wrapper once the seam lands).

What to do

• Implement the Method.prepare(repo, tools, *, gen) -> MethodResult(tools, canonicalize) seam in src/toolprobe/methods/.
• A method may only transform how the tool catalog is PRESENTED; the scorer stays frozen (adapt-then-canonicalize).
• No mlx import in methods/ (the hygiene test enforces this).
• Report gains on held-out cases/test.jsonl with non-overlapping CIs — do not select on test.

Acceptance

• toolprobe run --method <name> emits a comparison row; unit tests cover the transform + canonicalization.