feat: add confirmation-gated TaskMarket toolset

[a1271981054]

Related Issues

• fixes proposal: add confirmation-gated TaskMarket requester toolset #12341

Proposed Changes

This PR adds TaskMarketToolset, a first-party Haystack Toolset for discovering and requesting external TaskMarket work from an agent workflow.

• Adds read-only tools for listing tasks, retrieving task status, and reviewing submissions through the public API.
• Adds a preview tool that canonicalizes the request, calculates the Base USDC maximum spend including platform and relay fees, and returns a short-lived confirmation token.
• Adds a confirmation-gated create tool. It requires confirm=True, a matching preview, an application-provided approval callback, Base/USDC wallet preflight, and sufficient USDC balance.
• Uses the first-party taskmarket CLI without accepting private keys, shell interpolation, automatic submission acceptance/rejection, or retries of ambiguous writes.
• Adds serialization that preserves only safe read-capable configuration; runtime approval callbacks and wallet state are never serialized.
• Adds user documentation and a release note.

How did you test it?

• hatch run fmt
• hatch run test:types
• hatch run test:unit test/tools -q — 294 passed, 12 deselected
• hatch -e test run python -c 'from haystack.tools import TaskMarketToolset; ...' against the live public TaskMarket API — read-only listing succeeded.
• Manual taskmarket deposit and taskmarket stats output checks confirmed the Base chain, USDC contract, and balanceUsdc fields consumed by the preflight path.

Notes for the reviewer

The write path intentionally stops at an application approval callback and never handles private keys. A CLI timeout is reported as status="unknown" so callers reconcile live status before deciding whether to do anything else.

This PR was fully generated with an AI assistant. I have reviewed the changes and run the relevant tests.

Checklist

• I have read the contributors guidelines and the code of conduct.
• I have updated the related issue with the implementation and test evidence.
• I have added unit tests and updated the docstrings.
• I've used a conventional commit type for the PR title.
• I have documented the code and user-facing behavior.
• I have added a release note file.
• I have run the repository formatter and type checks.

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