docs: document GRAPHIFY_CLAUDE_CLI_MODEL (#2861)

The claude-cli backend defaults to Opus, so community naming can burn
Opus quota silently. Document the env var in the README environment
section and mention it in the label/cluster-only --model help.

README.md

@@ -410,6 +410,8 @@ Beyond your AI assistant, query `graph.json` straight from the CLI with `graphif
 
 Backends, API keys, hook behavior, and tuning are controlled by environment variables. Full table: **[Configuration](https://docs.graphify.com/reference/configuration)**.
 
+- **Claude CLI model**: `GRAPHIFY_CLAUDE_CLI_MODEL` overrides the model for the `claude-cli` backend (default: Opus). `haiku` or `sonnet` are usually enough for community naming; the semantic extraction pass benefits from a larger model.
+
 ---
 
 ## Privacy

graphify/__main__.py

@@ -909,13 +909,13 @@ def _run_cli() -> None:
         print("    --graph <path>          path to graph.json (default <path>/graphify-out/graph.json)")
         print("    --no-label              keep 'Community N' placeholders (skip LLM community naming)")
         print("    --backend=<name>        backend to use for community naming (default: auto-detect)")
-        print("    --model=<name>          model to use for community naming")
+        print("    --model=<name>          model to use for community naming (claude-cli also reads GRAPHIFY_CLAUDE_CLI_MODEL)")
         print("    --max-concurrency=N     parallel community-labeling LLM calls (default 4; forced to 1 for ollama/claude-cli)")
         print("    --batch-size=N          communities per labeling LLM call (default 100)")
         print("  label <path>            (re)name communities with the configured LLM backend, regenerate report")
         print("    --missing-only         keep existing labels and only name missing/placeholder communities")
         print("    --backend=<name>        backend to use (default: auto-detect from API keys)")
-        print("    --model=<name>          model to use for community naming")
+        print("    --model=<name>          model to use for community naming (claude-cli also reads GRAPHIFY_CLAUDE_CLI_MODEL)")
         print("    --max-concurrency=N     parallel labeling LLM calls (default 4; forced to 1 for ollama/claude-cli)")
         print("    --batch-size=N          communities per labeling LLM call (default 100)")
         print("  query \"<question>\"       BFS traversal of graph.json for a question")