* feat(agent-core): repair malformed tool args JSON
Attempt jsonrepair when tool call arguments fail JSON.parse, then continue schema validation. Return malformed JSON errors with a concise expected schema hint so the model can retry with corrected arguments.
* chore(nix): update pnpm deps hash
Update the fixed-output pnpmDeps hash after adding jsonrepair so the Nix build can fetch dependencies.
* refactor(agent-core): drop tool args JSON repair
Stop repairing malformed tool call arguments. Fall back to an empty object on JSON parse failure and let schema validation produce the retry error, while preserving valid arguments for unknown tools in the transcript.
* chore: add changeset for tool args validation
