Astrolabe (and any other PHP-side client) sends a stable User-Agent on
every outbound call to the MCP server. Capture it at the middleware
layer so backend access logs can attribute each request to a specific
client build — e.g. ``Nextcloud-Astrolabe/0.14.1``.
The middleware fires only for /api/v1/* and /webhooks/nextcloud,
which is the surface PHP-side clients hit; /mcp and /health stay
silent. The structured ``extra`` ({user_agent, http_method, http_path})
flows into OTel spans so the field is queryable in Grafana / Loki.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>