config-setlisted

# Config set Persist an engine-wide configuration value. The single key the engine reads today is `diff.tool` — the command `/skill-engine:review` prints when surfacing how to inspect a proposed-vs-live diff. The default value is `git diff --no-index --color`; users with a preferred diff tool override it once and the choice persists across sessions. ## Argument shape `/skill-engine:config-set <key> "<value>"` Example invocations: ``` /skill-engine:config-set diff.tool "delta" /skill-engine:config-set diff.tool "git diff --no-index --color" /skill-engine:config-set diff.tool "code --diff" ``` The `<value>` is taken verbatim; quote it so shell-splitting does not eat embedded spaces. The engine does not validate that the configured command exists on the user's PATH — that is the user's responsibility. A misconfigured command surfaces as a runtime failure when `/skill-engine:review` prints it and the user runs it. ## Resolution of the config file The config file lives at `$CLAUDE_PLUGIN_DATA/config.json`. The directory is created if absent. When `$CLAUDE_PLUGIN_DATA` is unset, surface: ``` $CLAUDE_PLUGIN_DATA is unset. The engine's plugin-data tree is not reachable from this shell. Run the skill from a Claude Code session where the plugin is installed, or set $CLAUDE_PLUGIN_DATA to the engine's plugin-data directory. ``` Exit non-zero. Do not write a config file to a fallback location — the engine's other surfaces (`/skill-engine:review`) key off `$CLAUDE_PLUGIN_DATA`,