fix(tests): Use record.message instead of record.msg in log assertions

Root cause: When we converted f-strings to %s format strings in logger.warning(),
the log record behavior changed:
- f-strings: record.msg contains the fully formatted string
- %s format: record.msg contains the template with %s placeholders
             record.message contains the formatted result

The test was checking record.msg which now contains the unformatted template
like 'Cannot set environment for new %s.' instead of the formatted message
like 'Cannot set environment for new windows.'

Fix: Changed assertions to use record.message (the proper way to access
formatted log messages) instead of record.msg.

Author: tony

tests/workspace/test_builder.py

@@ -457,7 +457,7 @@ def test_environment_variables_warns_prior_to_tmux_3_0(
         sum(
             1
             for record in caplog.records
-            if "Cannot set environment for new windows." in record.msg
+            if "Cannot set environment for new windows." in record.message
         )
         # From window_overrides and both_overrides, but not
         # both_overrides_in_first_pane.
@@ -467,7 +467,7 @@ def test_environment_variables_warns_prior_to_tmux_3_0(
         sum(
             1
             for record in caplog.records
-            if "Cannot set environment for new panes." in record.msg
+            if "Cannot set environment for new panes." in record.message
         )
         # From pane_overrides and both_overrides, but not both_overrides_in_first_pane.
         == 2
@@ -476,7 +476,7 @@ def test_environment_variables_warns_prior_to_tmux_3_0(
         sum(
             1
             for record in caplog.records
-            if "Cannot set environment for new panes and windows." in record.msg
+            if "Cannot set environment for new panes and windows." in record.message
         )
         # From both_overrides_in_first_pane.
         == 1