Add initial docs: dev log and version targets

Add docs/dev-log.md and docs/version-targets.md to seed project documentation. dev-log.md provides a development log and template for recording setup steps, decisions, current focus, status, and next steps. version-targets.md records primary target platform and exact Fallout 4/F4SE version targets, testing notes, and compatibility guidance to ensure consistent environment for early native plugin development.

docs/dev-log.md

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+# Development Log
+
+This file tracks the development progress of Fallout 4 Together.
+
+Use this log to record setup decisions, tool versions, technical discoveries, failed experiments, and successful tests.
+
+---
+
+## 2026-05-30
+
+### Repo Setup
+
+* Created the Fallout 4 Together repository.
+* Added the initial repository folder structure.
+* Added starter Markdown documentation files.
+* Added project roadmap, disclaimer, setup notes, protocol notes, and plugin planning documents.
+
+### Current Focus
+
+The current focus is setting up the early development environment before writing multiplayer logic.
+
+The immediate priority is to make sure the project has:
+
+* A documented target Fallout 4 version
+* A documented F4SE version
+* A chosen CommonLibF4 plugin template
+* A clean Fallout 4 test profile
+* A basic native plugin that can load through F4SE
+
+### Decisions Made
+
+* Project name: Fallout 4 Together
+* Internal prefix: F4T
+* Primary target platform: Steam Fallout 4
+* First prototype goal: two clients in a controlled test cell, with each player visible as a synced remote actor
+* Early test cell name: F4TTestCell01
+* Early test ESP name: Fallout4Together_Test.esp
+* Early plugin DLL name: Fallout4Together.dll
+
+### Current Status
+
+```text
+Repository created
+Documentation structure added
+Version tracking started
+No plugin code yet
+No server code yet
+No Creation Kit test cell yet
+```
+
+### Next Steps
+
+* Add `docs/version-targets.md` to the repository.
+* Fill in the exact installed Fallout 4 version.
+* Fill in the exact installed F4SE version.
+* Choose a CommonLibF4 plugin template.
+* Create the first GitHub milestones.
+* Create the first GitHub issues.
+* Set up a clean Fallout 4 test profile.
+* Build an empty F4SE plugin.
+* Confirm the empty plugin loads in Fallout 4.
+
+---
+
+## Template Entry
+
+Use this format for future updates:
+
+```markdown
+## YYYY-MM-DD
+
+### What Changed
+
+- 
+
+### What Worked
+
+- 
+
+### What Broke
+
+- 
+
+### Notes
+
+- 
+
+### Next Steps
+
+- 
+```

docs/version-targets.md

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+# Version Targets
+
+Fallout 4 Together is version-sensitive because it depends on Fallout 4, F4SE, and native plugin development.
+
+## Primary Target
+
+```text
+Platform: Steam
+Fallout 4 Version: 1.11.221.0
+F4SE Version: 1.11.221.0
+Creation Kit Version:
+CommonLibF4 Template:
+Compiler:
+Build System:
+```
+
+## Notes
+
+All multiplayer testing should use the same:
+
+* Fallout 4 version
+* F4SE version
+* Fallout 4 Together plugin version
+* Fallout 4 Together test ESP version
+* Load order
+* Test save
+
+## Secondary Targets
+
+```text
+GOG: Not currently tested
+Microsoft Store/Game Pass: Not supported
+Console: Not supported
+```
+
+## Reasoning
+
+F4SE supports the latest Fallout 4 versions available on Steam and GOG, but Steam and GOG are not always the same version. This means native plugin work should lock to one primary target during early development.
+
+## Current Development Decision
+
+Fallout 4 Together will use the Steam build of Fallout 4 as the primary development target.
+
+GOG support may be investigated later once the plugin loads successfully and the basic transform-sync prototype is working.
+
+## Compatibility Warning
+
+Fallout 4 Together may not work across different Fallout 4 executable versions.
+
+During testing, every connected player should use the same game version, F4SE version, plugin version, ESP version, and load order.