## Why
The TUI currently creates a shared plaintext `codex-tui.log` under the
default log directory. That append-only file can keep growing across
runs even though the TUI already records diagnostics in bounded local
stores.
Make the plaintext file log an explicit troubleshooting choice instead
of a default side effect.
This is possible because logs are also stored in the DB with proper
rotation
## What changed
- Only install the TUI file logging layer when `log_dir` is explicitly
set.
- Remove the prior `codex-tui.log` at startup before an opt-in file
layer is created.
- Clarify the `log_dir` config/schema text and `docs/install.md` example
so users opt in with `codex -c log_dir=...` when they need a plaintext
log.
jif-oai
f55f864b9f