Fix inconsistencies in "Transform" vs "Generate" tooltips for assistant v2 (#22160)

Also makes the inline assistant and inline terminal assistant share a
bunch more code.

Release Notes:

- N/A

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Co-authored-by: Agus <agus@zed.dev>
Co-authored-by: Agus Zubiaga <hi@aguz.me>

crates/assistant2/src/assistant.rs

@@ -6,6 +6,7 @@ mod context_picker;
 mod context_store;
 mod context_strip;
 mod inline_assistant;
+mod inline_prompt_editor;
 mod message_editor;
 mod prompts;
 mod streaming_diff;