complete codex docs

docs/decisions/0001-screen-vs-tmux.md

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+# Decision 0001: Keep `screen` As The Shared Backend
+
+## Status
+
+Accepted
+
+## Decision
+
+GSP should keep `screen` as the shared process/session backend for both Linux and Windows/Cygwin agents for the current platform generation.
+
+## Reasoning
+
+- The existing agents already implement server lifecycle around `screen`.
+- Linux and Windows/Cygwin behavior can stay aligned if both sides share the same session model.
+- The Panel already expects session-based lifecycle checks.
+- Moving to a different backend too early would create a large amount of compatibility work for start/stop/restart, logging, and scheduler flows.
+
+## Alternatives Considered
+
+- `tmux`
+- direct process supervision without session wrappers
+- custom daemon per server
+
+## Why Those Were Not Chosen
+
+- They would require broader code changes across both agents and the Panel.
+- The existing runtime, log, and scheduler flows already assume `screen`.
+- Cross-platform parity is easier to maintain with the current backend.
+