Add docs lifecycle flows

[chubes4]

Summary

• Add explicit bootstrap and maintenance flows for both technical and user documentation.
• Keep the existing technical-docs-flow and user-docs-flow slugs as maintenance aliases for current consumers.
• Update bundle prompts, workflow inputs, README guidance, example runner config, and bundle validation coverage for living documentation lifecycle modes.

Testing

• php tests/validate-docs-agent-bundle.php
• php -l tests/validate-docs-agent-bundle.php
• JSON syntax validation for bundle/example/test JSON files
• git diff --check

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (GPT-5.5)
• Used for: Drafted the lifecycle flow split, updated bundle metadata/docs/tests, and ran focused validation; Chris remains responsible for review and merge.