Don't steal focus when an agent spawns a child via MCP

CHANGELOG.md

@@ -20,6 +20,12 @@ loosely follows [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
   child agent, even though you were still within that thread.
 
 ### Changed
+- Agent-initiated `spawn_agent` and `spawn_process` MCP calls no
+  longer steal viewport focus from the currently active tab. The
+  new child still appears in the sidebar and tab bar; switch to it
+  explicitly via the palette or `select_process`. Palette-initiated
+  spawns and persistence restores are unchanged — they still auto-
+  focus the new pane.
 - Sidebar rows (Processes, Agent Tree, Scratchpads) now truncate
   overflowing names with a trailing `…` instead of spilling into
   the main viewport. The focused row marquees its name when it