feat(v1.0): interactive knowledge graph viewer with force-directed layout

[Pratiyush]

Why

The current `/wiki-graph` (v0.2) outputs a static `graph.json` + basic `graph.html`. It works but:

• No zoom/pan/search
• No clustering by project or entity type
• No node sizing by connection count (hub detection)
• No edge labels showing relationship type
• No dark mode support
• Can't click a node to navigate to the page
• Doesn't show on the main site (separate standalone file)

Karpathy's spec says: "Obsidian's graph view is the best way to see the shape of your wiki — what's connected to what, which pages are hubs, which are orphans." We should match that quality.

What

1. Upgrade `graph.html` to a full interactive viewer

• Force-directed layout (d3-force or sigma.js via CDN — no bundler needed)
• Zoom + pan with mouse/trackpad
• Node sizing proportional to inbound link count (hubs are big, orphans are tiny)
• Node coloring by type: sources (blue), entities (purple), concepts (green), syntheses (orange)
• Edge labels on hover showing the relationship text from `## Connections`
• Click to navigate — clicking a node opens the wiki page in a new tab
• Search overlay — type to highlight matching nodes (same as Obsidian's graph search)
• Cluster toggle — group nodes by project or by type
• Orphan highlighting — nodes with zero inbound links glow red

2. Embed in the main site

• New nav link: "Graph" → `site/graph.html`
• Or: embed as a widget on the home page (smaller, non-interactive preview that links to the full graph)

3. Dark mode

• Graph background + labels + edges must flip with the page theme toggle
• Use CSS vars from the existing `--bg` / `--text` / `--accent` palette

4. Stats overlay

• Total nodes / edges / clusters
• Average connections per page
• Top 5 hubs (most connected)
• Orphan count

Acceptance criteria

• `site/graph.html` renders an interactive force-directed graph
• Nodes are clickable → navigate to the page
• Search highlights matching nodes
• Dark mode matches the rest of the site
• Stats overlay shows hub/orphan counts
• Works offline (CDN-loaded JS with local fallback)
• No new Python deps (graph data is still built by `llmwiki graph`)
• Performance: renders 500+ nodes smoothly (WebGL preferred for large graphs)

Non-goals

• 3D graph (2D force-directed is enough for v1.0)
• Real-time editing of connections in the viewer
• Embedding inside Obsidian (users who want that use Obsidian's native graph)

Related

• `/wiki-graph` slash command (v0.2) already builds `graph.json`
• `llmwiki/graph.py` already walks `[[wikilinks]]` and outputs the node/edge data
• feat: reader-first article shell (Wikipedia-style page layout) #112 reader-first article shell (graph could be a panel in the reader)