Implemented /fork to fork the current session directly (no picker),
handling it via a new ForkCurrentSession app event in both tui and tui2.
Updated slash command descriptions/tooltips and adjusted the fork tests
accordingly. Removed the unused in-session fork picker event.
## Summary
- render tooltip content through the markdown renderer and prepend a
bold Tip label
- wrap tooltips at the available width using the indent’s measured width
before adding the indent
## Testing
- `/root/.cargo/bin/just fmt`
- `RUSTFLAGS="--cfg tokio_unstable" TOKIO_UNSTABLE=1
/root/.cargo/bin/just fix -p codex-tui` *(fails: codex-tui tests
reference tokio::time::advance/start_paused gated behind the tokio
test-util feature)*
- `RUSTFLAGS="--cfg tokio_unstable" TOKIO_UNSTABLE=1 cargo test -p
codex-tui` *(fails: codex-tui tests reference
tokio::time::advance/start_paused gated behind the tokio test-util
feature)*
------
[Codex
Task](https://chatgpt.com/codex/tasks/task_i_693081406050832c9772ae9fa5dd77ca)
