Implement the OpenCode Drafting Table MVP

Scope

Implement the first local Drafting Table integration using OpenCode and the reusable Specification Toolkit, with the eliciting-requirements skill as the initial consumer after #56/PR #64 is accepted.

The MVP should start or resume a session, invoke governed tools, present diagnostics and impact candidates, and stop at an explicit user approval boundary. It must not edit registered specification files directly.

Dependencies

• #28, #30, #33, and #34.
• #56/PR #64 skill implementation.
• ears-manager and project bootstrap child issues.

Acceptance criteria

• A fixture session can be replayed headlessly with stable inputs and outputs.
• Tool permissions and failure behavior are testable.
• Draft conversation state, authoritative Git state, and WMS state remain distinct.
• A recorded demonstration shows one approved or rejected change-set path.