memgraph v1.9.0 — cli-guide-spec discovery

Embedded agent guide

• memgraph guide emits the embedded cli-guide-spec JSON mental model
• memgraph guide --human renders the same guide as Markdown
• memgraph help-json exposes the complete machine-readable command catalog
• HTTP GET /guide serves the same envelope and GET /llms.txt provides an agent breadcrumb
• Discovery works offline/cold-start, including global flags before the command

Validated with go test ./..., go test -race ./..., go vet ./..., go build ./..., cold-start JSON/Markdown smoke, and invalid-argument exit checks.