feat: add Taskmarket delegation skill

[rajishere9]

Integration pitch

• Target: Bankr Skills, the official public skill repository used by Bankr agents.
• Surface: A new taskmarket skill and catalog entry, installed from GitHub.
• User flow: Discover open Taskmarket work without spending; inspect live task state and pendingActions; use the connected Bankr wallet for address-bound EIP-191 signatures; submit artifacts through Taskmarket's canonical presigned upload flow; monitor submissions and awards.
• Requester flow: Translate only the user's request into a task brief, preview reward/duration/visibility and the exact X402 spend, then create escrow or settle only after explicit authorization.
• Wallet design: Bankr Wallet API is the only signing surface; a free Taskmarket device token is optional and device-scoped. The skill never requests or stores a private key and never mixes payer and signer addresses.
• Files: taskmarket/SKILL.md, taskmarket/catalog.json.
• Safety: Task content and artifacts are untrusted; no automatic X402 payments, acceptance, rejection, rating, withdrawal, or legal acceptance; no secrets in artifacts; HTTPS-only presigned uploads and idempotency reconciliation.

Validation

• jq empty taskmarket/catalog.json
• git diff --check
• Live read-only validation against https://api.taskmarket.dev/api/tasks and GET /api/legal/current
• Confirmed the catalog demo uses the current Taskmarket list/get API shapes

This is a Bankr skill integration rather than a core Taskmarket code change, so there is no browser UI or screenshot to include. The Taskmarket implementation and raw API references are linked in the skill itself.