## Why
With the local model layer and app-server routing in place from PR1,
this PR moves the active TUI runtime onto app-server notifications. The
affected pieces share the same event flow, so the command surface,
session state, bottom-pane prompts, chat rendering, history/status
views, and tests move together to keep the stacked branch buildable.
This PR also removes the obsolete compatibility surface that is no
longer used after the migration. The proposed protocol-boundary verifier
layer was dropped from the stack; enforcing that final boundary will be
simpler once `codex-tui` no longer needs any `codex_protocol`
references.
This PR is part 2 of a 2-PR stack:
1. Add TUI-owned replacement models and extract app-server event
routing.
2. Move the active TUI flow to app-server notifications and delete
obsolete adapter code.
## What changed
- Rewired app command and session handling to use app-server request and
notification shapes.
- Moved approval overlays, request-user-input flows, MCP elicitation,
realtime events, and review commands onto the app-server-facing model
surface.
- Updated chat rendering, history cells, status views, multi-agent UI,
replay state, and TUI tests to use app-server notifications plus the
local models introduced in PR1.
- Deleted `codex-rs/tui/src/app/app_server_adapter.rs` and the
superseded `chatwidget/tests/background_events.rs` fixture path.
## Verification
- `cargo check -p codex-tui --tests`
- Top of stack: `cargo test -p codex-tui`
- Migrate apply-patch verification and application internals to use the
async `ExecutorFileSystem` abstraction from `exec-server`.
- Convert apply-patch `cwd` handling to `AbsolutePathBuf` through the
verifier/parser/handler boundary.
Doesn't change how the tool itself works.
This is a follow-up to https://github.com/openai/codex/pull/15922. That
previous PR deleted the old `tui` directory and left the new
`tui_app_server` directory in place. This PR renames `tui_app_server` to
`tui` and fixes up all references.
This is the part 1 of 2 PRs that will delete the `tui` /
`tui_app_server` split. This part simply deletes the existing `tui`
directory and marks the `tui_app_server` feature flag as removed. I left
the `tui_app_server` feature flag in place for now so its presence
doesn't result in an error. It is simply ignored.
Part 2 will rename the `tui_app_server` directory `tui`. I did this as
two parts to reduce visible code churn.
Migrate `cwd` and related session/config state to `AbsolutePathBuf` so
downstream consumers consistently see absolute working directories.
Add test-only `.abs()` helpers for `Path`, `PathBuf`, and `TempDir`, and
update branch-local tests to use them instead of
`AbsolutePathBuf::try_from(...)`.
For the remaining TUI/app-server snapshot coverage that renders absolute
cwd values, keep the snapshots unchanged and skip the Windows-only cases
where the platform-specific absolute path layout differs.
