fix(tests): stop the checkout location and system zshrc from failing tests

Three tests fail on a clean checkout depending on where the repo lives and
which terminal runs the suite:

- status-line-path builds its fake home inside the checkout, so a clone under
  /tmp lands in a SCRATCH_ROOTS prefix and renders the scratch icon.
- status-line/component renders a fixed 120 columns, so a long checkout path
  or branch name pushes the cost segment out of the assertion.
- bash-executor runs an interactive login zsh, which loads the system
  /etc/zshrc; under Apple Terminal that appends session-save lines to the
  captured output. HOME does not isolate a system-level file.

packages/coding-agent/test/bash-executor.test.ts

@@ -438,6 +438,13 @@ exit 64
 			env: {
 				PATH: Bun.env.PATH ?? "",
 				HOME: shellDir,
+				// The command runs through an interactive login zsh, which loads the
+				// system `/etc/zshrc`. On macOS that pulls in
+				// `/etc/zshrc_Apple_Terminal`, and under Apple Terminal it appends
+				// "Saving session..." lines to the captured output on exit. `HOME`
+				// does not isolate a system-level file; this is the opt-out Apple
+				// documents in that script.
+				SHELL_SESSIONS_DISABLE: "1",
 			},
 			prefix: undefined,
 		});