feat(visualize): add --canvas flag for Cursor topology view

[fmenesesg]

Proposed change

Add a simple client-facing workflow to generate an interactive Cursor IDE topology canvas from any 3scale export, alongside the existing Markdown report.

Clients run one command:

threescale-visualize ./export -o ./report --canvas ./topology.canvas.tsx

Then copy the file to ~/.cursor/projects/<workspace>/canvases/ and open it in Cursor.

Type of change

• New feature
• Documentation
• Tests / CI

RHCL checklist

• Tests added or updated (go test ./...)
• CI does not introduce -DskipTests without justification
• No secrets in diff (tokens, kubeconfigs, OIDC secrets)
• PR description and docs in English
• Tested against export-minimal fixture

Summary

• --canvas flag on threescale-visualize writes a self-contained .canvas.tsx with embedded export data
• Policy chains fall back to proxy.json (policies_config) when policies.json is empty
• Fixture demo at docs/examples/topology-demo.canvas.tsx (no customer data)
• docs/VISUALIZE.md documents report + canvas workflow and Cursor setup

Changes

File	Change
internal/visualize/canvas_data.go	Build compact canvas payload from tenant export
internal/visualize/canvas.go	Embed template and write .canvas.tsx
internal/visualize/canvas/topology.canvas.tsx.tmpl	Generic topology canvas (charts, graph, sortable table)
internal/visualize/cli/cli.go	--canvas flag
internal/visualize/loader.go	Policy chain fallback from proxy.json
docs/examples/topology-demo.canvas.tsx	Demo from export-minimal fixture
docs/VISUALIZE.md	Client workflow + Cursor instructions
docs/TEST_CASES.md	TC-VIZ-004

Test plan

• go test ./...
• threescale-visualize internal/visualize/testdata/export-minimal --canvas docs/examples/topology-demo.canvas.tsx
• Generated demo contains seed_alpha, no customer references