fix(text): the tests and docs follow the layer being kept

Review of the first commit found three places that still asserted the old cleanup: the UI integration
test (which would have failed CI), docs/agents.md, and the comments on TextEdit::created, layer.newText
and the engine test itself.

Co-Authored-By: DeepSeek V4.1 Flash <noreply@deepseek.com>

crates/engine/src/cmd/layer/create.rs

@@ -161,7 +161,7 @@ pub(super) fn text_range_p(p: &Value) -> Option<std::ops::Range<usize>> {
 /// It is left justified unless `justify` is given. The layer is named by `name`, else the first 40
 /// characters of the first text line, else "Text". `edit: true` also opens a new editing
 /// session with anchor `0` and the caret after the text, selecting all initial text so the next
-/// insertion replaces it. The session has `created: true`, so leaving it empty removes the layer.
+/// insertion replaces it. The session has `created: true`; leaving it empty keeps the layer, as After Effects does.
 pub(super) fn new_text(s: &mut Session, p: &Value) -> Result<Value> {
     let cid = comp_id(s, p)?;
     let comp = s.project.comp(cid).ok_or(EngineError::NoComp)?.clone();

crates/engine/src/cmd/text_edit.rs

@@ -71,7 +71,8 @@ pub struct TextEdit {
     /// Character panel changes made with only a caret: the style the next typed text takes.
     #[serde(default)]
     pub pending: Option<CharStyle>,
-    /// The layer was made by a Type tool click; leaving it empty deletes it.
+    /// The layer was made by a Type tool click. Kept when left empty, as After Effects does, so this
+    /// only records how the edit began.
     #[serde(default)]
     pub created: bool,
     /// Line position kept by repeated up / down moves (layout space).