docs(adr): add ADR-0011 'Actions as AI Tools (Operational Parity)'

Proposes that every Action opts in to AI exposure via a single `ai:` block
on ActionSchema, and the runtime auto-derives AIToolDefinitions from the
existing ActionRegistry. Eliminates the need to maintain parallel skill /
tool code for every business operation an admin can already perform.

- Adds opt-in `ai: { exposed, description, paramHints, outputSchema, ... }`
  block to @objectstack/spec ui/action.zod.ts
- Adds ActionRegistry.toolsForAi(opts) in @objectstack/runtime
- Wires service-ai/agent-runtime to merge action-tools into availableTools
- Routes LLM tool_calls with meta.kind='action' through ActionRegistry so
  permissions, validation, hooks, audit, and transactions all apply uniformly
- Confirmation defaults derived from existing confirmText / type='delete'

Authored from HotCRM v1.1 planning. HotCRM will be the first consumer:
delete src/skills/, convert each business skill to defineAction with ai
exposed, ship the 'Operational Parity' story as Wow #4.

Refs ADR-0003, ADR-0008, ADR-0009, ADR-0010.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: os-zhuang