refactor(tui): prompt deep-module PR 6 — façade reduction + verification

CHANGELOG.md

@@ -15,6 +15,7 @@ GitHub Releases page; `0.8.0` is the new starting line.
 
 ## Unreleased
 
+- Reduce the shell prompt session to a compatibility façade over deep `prompting/` modules (config, keybindings, completion menus, narrow shell-facing methods), with Unicode cell-width coverage and documented module ownership in the architecture guide.
 - Render image/audio/video and unknown content parts as payload-free labels in the live view, roll nested subagent activity (up to 16 levels) under the correct root tool card, and stop provider-remapped tool results from starting replay user turns.
 - **Behavior change:** `!` shell commands now run through the detected configured shell (`<shell> -c`, PowerShell `-command` on Windows) instead of the implicit `/bin/sh`/`cmd.exe`, with separate 1 MiB stdout/stderr caps and cancellation cleanup; existing `cmd.exe`-syntax commands on Windows may need updating.
 - Distinguish background auto-trigger grace expiry from user input activity with typed prompt events, and bound streamed tool-argument label scans to 1 KiB growth boundaries.

docs/en/customization/architecture.md

@@ -231,6 +231,33 @@ events include `StepBegin`, `StepRetry`, `StepInterrupted`, `ToolExecutionStarte
 The shell can run with a working directory inside its subtree, so `src/pythinker_code/ui/`
 is a candidate for a focused nested guide on prompt, visualization, and component layout.
 
+### Shell prompt deep modules
+
+`src/pythinker_code/ui/shell/prompt.py` is a compatibility façade: it keeps the public
+`CustomPromptSession` surface and re-exports legacy underscore helper names, while the
+implementation lives in the `src/pythinker_code/ui/shell/prompting/` deep modules.
+
+| Path | Owns |
+| --- | --- |
+| `prompting/frame.py` | One-frame snapshot flow: `PromptFrameCollector` samples every render delegate exactly once per frame into an immutable `PromptFrame`. |
+| `prompting/state.py` | Reducer-style prompt state: UI events flow through the reducer; render code reads state, never mutates it. |
+| `prompting/lifecycle.py` | Async task ownership and closers: startup/shutdown symmetry for session-owned background tasks. |
+| `prompting/renderer.py` | Scene row allocation and rendering within the terminal height/width budget (cell-width measured). |
+| `prompting/footer.py` | `FooterViewModel` plus content precedence and cell-width truncation, consumed by both toolbar adapters (pythinker and card styles). |
+| `prompting/toasts.py`, `git_status.py`, `history.py`, `clipboard.py` | Session-owned resources: toast queue, Git status snapshots, prompt history persistence, clipboard integration. |
+| `prompting/config.py` | `PromptConfig` / `PromptProviders`: constructor-time wiring of callbacks and providers. |
+| `prompting/keybindings.py` | `build_prompt_key_bindings` over the `PromptController` protocol. |
+| `prompting/completion/` | Canonical `CompletionContext`, slash-command completion, workspace-indexed `@` file mentions, and completion menus. |
+
+Workspace and Git snapshots publish asynchronously under a generation counter: each refresh
+owns its generation, and results from a superseded generation are discarded rather than
+rendered stale.
+
+Compatibility policy: legacy underscore helper names re-exported from `prompt.py` delegate to
+the session modules and remain import-compatible, but private implementation helpers are not
+supported extension interfaces and may change without notice; extend via the documented
+public surfaces (`CustomPromptSession`, `PromptConfig`/`PromptProviders`, tool renderers).
+
 ## ACP server
 
 | Path | Purpose | Key entry points and interfaces |

src/pythinker_code/ui/shell/__init__.py

@@ -2081,8 +2081,7 @@ def _maybe_present_pending_approvals(self) -> None:
     def _get_default_buffer_text_and_cursor(self) -> tuple[str, int]:
         if self._prompt_session is None:
             return "", 0
-        buf = self._prompt_session._session.default_buffer  # pyright: ignore[reportPrivateUsage]
-        return buf.text, buf.cursor_position
+        return self._prompt_session.input_state()
 
     def _activate_prompt_approval_modal(self) -> None:
         if self._prompt_session is None:
@@ -2101,7 +2100,7 @@ def _activate_prompt_approval_modal(self) -> None:
                 current_request,
                 on_response=self._handle_prompt_approval_response,
                 buffer_state_provider=self._get_default_buffer_text_and_cursor,
-                text_expander=self._prompt_session._get_placeholder_manager().serialize_for_history,  # pyright: ignore[reportPrivateUsage]
+                text_expander=self._prompt_session.serialize_for_history,
             )
             self._prompt_session.attach_modal(self._approval_modal)
         else: