feat: bind workspace actions to rendered state — 0.9.1

[silversurfer562]

Summary

• add a strict, non-executable workspace document grammar with widget and Markdown renderers
• bind returned actions to host-generated workspace id, revision, SHA-256 contract hash, and one-render nonce
• expose workspace render/collect MCP tools while leaving authorization and nonce consumption with the host
• release the API as attune-forms 0.9.1

Safety contract

The collector validates only that an action belongs to the rendered view and matches its binding. It does not execute, authorize, or consume the action. Host applications retain canonical state and authority.

Verification

• 874 tests passed
• full pre-commit suite passed
• package sdist and wheel built successfully
• Antigravity cross-review: clean, 11 files sent, 0 omitted, 0 findings

Downstream

Required by the attune-ai dynamic Fix workspace. Publishing 0.9.1 remains a separate post-merge approval.