feat(image-compare): add SSIM as parallel diff signal

CLAUDE.md

@@ -49,3 +49,40 @@ When modifying this repo:
 - Skills should be self-contained instructions that work without user interaction where possible
 - Agents should encode domain knowledge that would take multiple files to discover, not generic advice
 - Keep specialist agents in `agents/example-specialists/` to separate them from the generic set
+
+<!-- CODEGRAPH_START -->
+## CodeGraph
+
+CodeGraph builds a semantic knowledge graph of codebases for faster, smarter code exploration.
+
+### If `.codegraph/` exists in the project
+
+**Use codegraph tools for faster exploration.** These tools provide instant lookups via the code graph instead of scanning files:
+
+| Tool | Use For |
+|------|---------|
+| `codegraph_search` | Find symbols by name (functions, classes, types) |
+| `codegraph_context` | Get relevant code context for a task |
+| `codegraph_callers` | Find what calls a function |
+| `codegraph_callees` | Find what a function calls |
+| `codegraph_impact` | See what's affected by changing a symbol |
+| `codegraph_node` | Get details + source code for a symbol |
+
+**When spawning Explore agents in a codegraph-enabled project:**
+
+Tell the Explore agent to use codegraph tools for faster exploration.
+
+**For quick lookups in the main session:**
+- Use `codegraph_search` instead of grep for finding symbols
+- Use `codegraph_callers`/`codegraph_callees` to trace code flow
+- Use `codegraph_impact` before making changes to see what's affected
+
+### If `.codegraph/` does NOT exist
+
+At the start of a session, ask the user if they'd like to initialize CodeGraph:
+
+"I notice this project doesn't have CodeGraph initialized. Would you like me to run `codegraph init -i` to build a code knowledge graph?"
+<!-- CODEGRAPH_END -->
+# graphify
+- **graphify** (`~/.claude/skills/graphify/SKILL.md`) - any input to knowledge graph. Trigger: `/graphify`
+When the user types `/graphify`, invoke the Skill tool with `skill: "graphify"` before doing anything else.