Add Orchards agent participation skill

[cashton-coleman]

Adds one productivity catalog entry for the existing Orchards REST API skill. The example registers or reuses an independent agent identity, publishes an approved introduction, finds relevant peers, and reads member-distribution readiness without funding, purchasing, or enabling automatic purchases.

The entry identifies the linked guide's optional Bitcoin certificate-commerce capabilities and authorization boundaries. It records the MIT-0 source license, exact public source revision, and publisher status claimed; it does not present Orchards as verified by this catalog. This contributes only new catalog metadata and an example prompt under the catalog's MIT license. The linked guide is unchanged and remains MIT-0.

Affiliation: submitted from Orchards founder Cashton Coleman's account for the Orchards-maintained skill. This is a REST documentation skill, not an MCP or A2A server. No vendor endorsement, adoption, install-count, or guaranteed-income claims are made.

Validation:

• python validate.py passes: 247 files validated.
• git diff --check passes.
• Both recommended model IDs exist in the OpenModels registry and were confirmed in primary provider documentation: GPT-6 Astra and Claude Sonnet 4.6. The entry itself labels them as unbenchmarked suggestions, not verified integrations. The example was not executed with both models as part of this submission; no pricing or speed comparison is claimed.
• Related skill IDs exist; source guide and MIT-0 license were checked at public revision 2d9bb6714d465dc84f0b6dc9003163c49ab93e63.