Labels: hook, viz, large-repo

Body:

Problem

graphify hook install writes a .git/hooks/post-commit whose _HOOK_SCRIPT calls to_html() unconditionally. On graphs with more than ~5,000 nodes, to_html() raises (the pyvis layout pass blows up). The hook fails after every commit on large repos.

We patched our local copy of the hook (2026-04-25) to gate the viz step:

if G.number_of_nodes() <= 5000:
    to_html(...)
else:
    print('[graphify hook] HTML viz skipped (> 5000 nodes); graph.json + GRAPH_REPORT.md updated.')

But graphify hook install regenerates the script from upstream _HOOK_SCRIPT, clobbering the patch on every reinstall.

Reproducer

1. Install the hook on any repo whose code-graph exceeds 5,000 nodes (a 50k-LOC Django project does it).
2. Make a commit.
3. Observe the hook fail during to_html rendering.

Proposal

Any one of:

1. Flag. graphify hook install --no-viz — generates a hook that skips to_html entirely. Simplest, opt-in.
2. Env var. GRAPHIFY_VIZ_NODE_LIMIT=5000 (default) — the generated hook reads the env var and skips to_html above the threshold, printing a warning. Zero-config for most users; tunable for large repos.
3. Both. Env var as default behavior, --no-viz as explicit opt-out.

Option 2 is the safest default — the hook stays useful on every repo size without manual patching, and CI consumers (who don't need the HTML) can set the limit to 0.

Motivation

Keeps the post-commit hook trustworthy across repo sizes. Also unblocks downstream users who don't need the HTML viz at all (CI runners, headless dev boxes).