fix(graph): scope CSS to #graph and add fit-to-view for HTML viewer

[A3Ackerman]

Summary

bd graph --html is unusable on non-trivial graphs: the legend covers the viewport and graph nodes run off-screen even after Reset View. Two distinct bugs in the embedded HTML template:

1. CSS scope blow-up. svg { width: 100vw; height: 100vh } matches every <svg> on the page — including the 30×10 legend swatches for "blocks" and "parent-child" edge types. Each swatch balloons to viewport size, stretching the #legend container to ~1500×1600 and covering the graph. Fix: scope to #graph.
2. Initial-zoom does not actually fit. d3.zoomIdentity.translate(width/4, height/4).scale(0.8) is a fixed transform that doesn't read node positions; multi-layer graphs (x = 150 + layer*220) push deep-layer nodes off-screen to the right. Fix: real fitToView() that reads the post-simulation bounding box and transforms to fit with padding. Adds a "Fit View" button and repoints resetZoom() to it so the existing Reset View button behaves as users expect.

Template-only change. No public API surface, no behavior change for the DOT renderer.

Why

Continuation of recent graph-viewer fixes:

• fix(graph): merge components for bd graph --all --html (GH#3592) #3648 (merged): single document for --all --html
• fix(graph): emit [] not null for empty links in HTML output (GH#3592) #3671 (merged): emit [] not null for empty links

This addresses the remaining unusability of the rendered viewer itself. Followed CONTRIBUTING.md "one issue per PR" — did not bundle the adjacent observation that --all --html still emits N sub-graphs per connected component (that is a layout choice, not a CSS bug; happy to file separately).

Verification

• Manually rendered against a real graph: legend ~134×190 (was ~1500×1600), graph auto-fits on initial render and on Reset View. Reproduced the bug + verified the fix on macOS Chrome.
• make build — clean
• golangci-lint run --build-tags gms_pure_go ./cmd/bd/... — 0 issues.
• make test — hits an environmental hang in internal/utils/TestMain (testutil.EnsureDoltContainerForTestMain) on my local box, unrelated to a Go HTML template string change. I expect CI (with Docker) to run this cleanly; happy to investigate further if it doesn't.

Notes for reviewers

• setTimeout(fitToView, 1500) rather than simulation.on("end", ...) — force simulations with strong charges don't naturally reach end without explicit alpha/alphaTarget discipline. The 1500ms heuristic works in practice; happy to revisit.
• fitToView() caps scale at the existing zoom.scaleExtent([0.1, 4]) upper bound (Math.min(width/bboxW, height/bboxH, 4)).
• Initial analysis and patch design by Syl (qcore crew); applied and verified upstream by me.

🤖 Generated with Claude Code

[maphew]

Thanks for the report. I’m doing a repro sweep and couldn’t find a concrete reproduction recipe in the current description or thread.

Could you add the smallest command sequence or setup that triggers this, including the bd version, storage mode, OS, and the expected vs. actual output? A scratch-repo repro is ideal if one is possible.

codex-gpt-5.5-medium on behalf of matt wilkie