Add JSON and HTML render formats

[lancekrogers]

Summary

Adds two new output formats to camp-graph render alongside the existing DOT, SVG, and PNG:

• --format json — Versioned envelope ({version, nodes, edges}) with deterministic sort order, suitable for piping into jq or feeding custom visualizations (vis.js, d3, Cytoscape, etc.). Reuses the existing json struct tags on graph.Node and graph.Edge.
• --format html — Self-contained browser-viewable document with inlined SVG. No JavaScript, no CDN, no external fonts. Includes a node-type legend, node/edge count summary, and prefers-color-scheme light/dark support.

Zero new dependencies — both formats build on the stdlib (encoding/json, html/template, embed) and the existing go-graphviz pipeline (HTML reuses RenderGraphviz to produce the embedded SVG).

Design highlights

• Deterministic JSON. Nodes sorted by ID, edges sorted by (from, to, type). Re-rendering the same graph produces byte-identical output — enables diffable artifacts and reliable round-trip tests.
• Schema versioning. JSON envelope includes a "version": "1" field so consumers can detect breaking shape changes.
• Shared palette. Renamed unexported styleForNode → StyleForNode so the HTML legend reuses the same color mapping as DOT/SVG/PNG — single source of truth.
• Template via embed.FS. templates/graph.html.tmpl is embedded at build time; no runtime filesystem dependencies.
• Stdout behavior. JSON streams to stdout like DOT (for | jq pipelines). HTML requires --output or the default .campaign/graphs/ auto-save, matching SVG/PNG semantics.

Changes

File	Change
internal/render/format.go	Add FormatJSON, FormatHTML + parse cases
internal/render/json.go	New — RenderJSON with deterministic sort
internal/render/html.go	New — RenderHTML with legend + inlined SVG
internal/render/templates/graph.html.tmpl	New — embedded HTML template
internal/render/renderer.go	Dispatch for JSON and HTML
internal/render/dot.go	Export StyleForNode for cross-renderer use
cmd/camp-graph/root.go	Flag help, stdout branch widening
README.md	Usage examples for new formats
internal/render/*_test.go	Full test coverage for both new formats

Test plan

• just lint — fmt + vet clean
• just test unit — 68/68 tests pass (5 new across render package)
• just build — clean binary
• Smoke: camp-graph render -f json --no-save | jq '{version, node_count: (.nodes|length)}' → {"version": "1", "node_count": 934} on real campaign
• Smoke: camp-graph render -f html -o /tmp/g.html → 1.1MB self-contained file, renders correctly in browser
• Regression: -f dot, -f svg, -f png all unchanged
• Error path: -f html --no-save without --output returns clear error
• No new entries in go.mod / go.sum

Example output

$ camp-graph render -f json --no-save | jq '.version, (.nodes|length), (.edges|length)'
"1"
934
722

$ camp-graph render -f html -o campaign.html && open campaign.html

[obey-agent]

Verdict: Approve

Overview:
This PR adds json and html render formats in the right place: the new behavior stays isolated to the render layer, keeps the CLI surface coherent, and does not introduce new dependencies or release-process churn. I re-ran the repo gates locally and smoke-tested both formats against the live campaign graph; the implementation is production-ready.

Key Findings:

• No blocking findings.

What's Done Well:

• JSON output is deterministic and wrapped in a versioned envelope, which is the right contract for downstream tooling.
• HTML rendering reuses the existing Graphviz/SVG path and the existing node-style palette instead of creating a parallel rendering stack.
• Tests cover parser changes plus JSON/HTML renderer behavior, and the branch also passed just lint, just test unit, and just build locally.
• Smoke validation succeeded with camp-graph render -f json --no-save | jq ... and camp-graph render -f html -o ... against the real campaign graph.

Residual Risk:

• HTML correctness is covered structurally rather than visually; if the team wants stronger regression protection later, the next step would be a snapshot or browser-level golden check for the generated HTML/SVG.

Staff Standard:
Yes. I would be comfortable submitting this as my own work.