harness 0.12.0

Changed

• Honor named agents' model and effort declarations on delegate requests, resolve model aliases
  through the selected provider, and preserve parent settings, tool restrictions and shared budgets.
• Update the embedded confinement boundary to Substrate 4d830f2f (package 0.7.6, development
  wire 0.16.0), which leaves Git metadata untouched when Git sources are disabled, and the
  outbound MCP client and testkits to 3c68df04 (0.1.1).
• Move the real Agentplugins skill and agent compatibility suite to Atlas, removing the reverse consumer dependency from Harness tests and CI.
• Publish source through standalone bot tooling without an Atlas checkout or dependency-admission
  requirement; retain Harness's own correctness checks and release requirements.

This source release was cut without running gates, tests or binary packaging, at the operator's
request. Existing historical test observations above are not new verification of this release.