Fixes two related input-handling bugs in the onboard wizard:
1. _input_text treated "" as None, preventing users from clearing
optional string fields or entering empty strings intentionally.
2. _input_model_with_autocomplete used `if value else None`, which
discarded falsy values such as empty strings or 0.
To support clearing optional string fields, add _is_str_or_none() and
normalize empty strings to None inside _configure_pydantic_model only
when the field annotation is `str | None`. Required str fields keep
"" as a valid value.
Also included:
- Remember last selected item in provider/channel/model menus for
better UX when configuring multiple items.
- Rename _SIMPLE_TYPES and _MENU_DISPATCH to lowercase to follow
Python naming conventions (they are local variables, not constants).
- Remove unused imports in test file.
Extracted from PR #3358.
Literal["standard", "persistent"] fields are now rendered as select
dropdowns instead of free-text input. This makes provider_retry_mode
and any future Literal fields self-documenting in the wizard.
- Add [H] Channel Common menu to configure send_progress, send_tool_hints,
send_max_retries, and transcription_provider
- Add [I] API Server menu to configure host, port, timeout
- Add real-time Pydantic field constraint validation (ge/gt/le/lt/min_length/max_length)
with constraint hints shown in field display (e.g. "Send Max Retries (0-10)")
- Add _pause() to View Configuration Summary to prevent immediate screen clear
- Fix _format_value dict branch to handle BaseModel instances without crashing
