docs: clarify runtime config paths for host and Docker usage

.gitignore

@@ -8,5 +8,4 @@
 /scanslicer.egg-info/
 /build/
 /appimage/
-.env
-/.scanslicer/
+.env

README.md

@@ -30,7 +30,7 @@ Project dependencies (from `pyproject.toml`):
 
 ## Quick Start
 
-### Run with `uv` (recommended for local dev)
+### Run with `uv`
 
 ```bash
 uv sync --frozen
@@ -87,16 +87,21 @@ Only locked boxes are exported.
 
 ## Data and Config Files
 
-Default host paths:
+Persistence paths depend on how ScanSlicer is run.
+
+Non-container runs (`uv run scanslicer`, `python -m scanslicer`):
 
 - Defaults: `~/.config/scanslicer/defaults.json`
 - Named presets: `~/.config/scanslicer/presets.json`
 - Auto-tune feedback: `~/.config/scanslicer/autotune-feedback.json`
 - Session status log: `~/.config/scanslicer/status.log`
 
-Container behavior:
+If `XDG_CONFIG_HOME` is set, these are stored under `$XDG_CONFIG_HOME/scanslicer/` instead.
+
+Container runs:
 
 - When running in container and `/work` exists, these are stored under `/work/.scanslicer/`.
+- In the provided `docker-compose.yml`, the current repository is mounted as `/work`, so these files appear in `.scanslicer/` inside the project directory on the host.
 
 Environment variable overrides: