Add Fallout 4 path resolver and update deploys

Introduce resolve-fallout4-path.bat to centralize locating the Fallout 4 installation. deploy-all.bat and deploy-ui.bat now call the resolver (accept an optional path arg or prompt interactively), and the chosen path is saved to a local .fallout4-path file (added to .gitignore). Updated docs (docs/dev-log.md, plugin/setup.md) to reflect the new behavior and usage examples. The resolver normalizes game or Data paths, probes common Steam locations, prompts the user when needed, and exports F4_DIR and DATA_DIR for callers.

docs/dev-log.md

@@ -7,6 +7,34 @@ failed experiments, successful tests, and next steps.
 
 ---
 
+## 2026-06-11 - Portable Fallout 4 Deploy Paths
+
+### Summary
+Deploy batch files now prompt for the Fallout 4 install location instead of hardcoding a single machine's Steam library path. The chosen path is saved locally in `.fallout4-path` for later runs.
+
+### Files Changed
+- `resolve-fallout4-path.bat` (new)
+- `deploy-all.bat`
+- `deploy-ui.bat`
+- `.gitignore`
+- `plugin/setup.md`
+
+### Details
+- Shared resolver accepts an optional command-line path (game root or `Data` folder)
+- On first run, tries saved path, common Steam locations, then prompts
+- `build-all.bat` unchanged; it forwards optional path args to `deploy-all.bat`
+
+### Testing
+- Batch scripts not run in this session
+
+### Known Issues
+- None currently known
+
+### Next Steps
+- Run `deploy-all.bat` on a machine without the old default path and confirm prompting/save behaviour
+
+---
+
 ## 2026-06-11 - Ultralight SDK Submodule
 
 ### Summary