feat: Add comprehensive Cloudflare Workflows integration documentation

Significantly expands the Workflows integration documentation based on PR 799
in the cloudflare/agents repository. This update transforms the basic workflow
triggering guide into comprehensive documentation covering:

- New AgentWorkflow base class for typed Agent access
- Complete API reference for workflow methods and lifecycle callbacks
- Automatic workflow tracking in Agent SQLite database
- Bidirectional communication patterns (Agent ↔ Workflow)
- Human-in-the-loop approval flows with convenience methods
- Progress reporting with custom progress types
- State synchronization between Workflows and Agents
- Common patterns: background processing, retries, approvals
- Best practices and limitations

Synced from: cloudflare/agents#799

Co-Authored-By: Claude Sonnet 4.5 <[email protected]>

Author: github-actions[bot]

cloudflare-docs

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+Subproject commit c44040312286dd926d1be74d495016d0b0e08c13