Add AI-driven prepare-providers-documentation skill (#65882)

* Add AI-driven prepare-providers-documentation skill

Add a Claude Code skill that replaces the manual commit-by-commit
classification step in `breeze release-management
prepare-provider-documentation` with AI-driven analysis. The skill
inspects every PR using sub-agents, scopes multi-provider PRs to the
current provider's slice, applies an explicit breaking-change checklist
against the actual diff, asks the release manager only when uncertain,
and covers both the initial classification and the rebase-time
incremental update flow.

Auto-generated build files are still regenerated by breeze under the
hood, so the skill stays consistent with existing release tooling. The
interactive breeze command remains documented as a fallback.

* Address review feedback on prepare-providers-documentation skill

- Scope breaking-change checklist's "public symbol removed/renamed" rule
  to the actual public-interface paths (hooks, operators, sensors,
  triggers, notifications, decorators, executors, top-level package, and
  anything referenced from provider.yaml) so internal helpers like
  utils/, _internal/, or pod_manager.py don't auto-trigger BREAKING_RISK.
- Extend "schema change in stored data" rule to cover the serialized
  state/context of BaseTrigger subclasses, so changes that would break
  deferred tasks running across a provider upgrade are flagged.
- Document prerequisites in dev/README_RELEASE_PROVIDERS.md: the skill
  needs an agentic coding framework with the GitHub MCP server
  configured. Show install steps for Claude Code and OpenAI Codex CLI.
- Generalise README references so the skill is presented as
  framework-neutral (loaded by Claude Code, OpenAI Codex CLI, or any
  MCP-compatible client that discovers SKILL.md from .claude/skills/),
  rather than Claude Code-exclusive.

Author: potiuk