Add a worktree loader test for being in a submodule

A submodule's git dir doesn't live inside its working tree, and `git
worktree list` reports it by its git dir. Lazygit compares that against
the working tree path, so it recognizes neither the current nor the main
worktree, and the UI ends up claiming we're in a linked worktree.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

pkg/commands/git_commands/worktree_loader_test.go

@@ -192,6 +192,48 @@ branch refs/heads/mybranch-worktree
 			},
 			expectedErr: "",
 		},
+		{
+			testName: "In a submodule",
+			repoPaths: &RepoPaths{
+				repoPath:           "/path/to/repo/mysubmodule",
+				worktreePath:       "/path/to/repo/mysubmodule",
+				repoGitDirPath:     "/path/to/repo/.git/modules/mysubmodule",
+				worktreeGitDirPath: "/path/to/repo/.git/modules/mysubmodule",
+			},
+			before: func(runner *oscommands.FakeCmdObjRunner, fs afero.Fs, getRevParseArgs argFn) {
+				// A submodule's git dir doesn't live inside its working tree, and
+				// `git worktree list` reports the git dir rather than the working
+				// tree it belongs to.
+				runner.ExpectGitArgs([]string{"worktree", "list", "--porcelain"},
+					`worktree /path/to/repo/.git/modules/mysubmodule
+HEAD d85cc9d281fa6ae1665c68365fc70e75e82a042d
+branch refs/heads/mybranch
+`,
+					nil)
+
+				gitArgs := append(append([]string{"-C", "/path/to/repo/.git/modules/mysubmodule"}, getRevParseArgs()...), "--absolute-git-dir")
+				runner.ExpectGitArgs(gitArgs, "/path/to/repo/.git/modules/mysubmodule", nil)
+
+				_ = fs.MkdirAll("/path/to/repo/.git/modules/mysubmodule", 0o755)
+			},
+			expectedWorktrees: []*models.Worktree{
+				{
+					/* EXPECTED:
+					IsMain:        true,
+					IsCurrent:     true,
+					ACTUAL: */
+					IsMain:        false,
+					IsCurrent:     false,
+					Path:          "/path/to/repo/.git/modules/mysubmodule",
+					IsPathMissing: false,
+					GitDir:        "/path/to/repo/.git/modules/mysubmodule",
+					Branch:        "mybranch",
+					Head:          "d85cc9d281fa6ae1665c68365fc70e75e82a042d",
+					Name:          "mysubmodule",
+				},
+			},
+			expectedErr: "",
+		},
 		{
 			testName: "Detached HEAD worktree",
 			repoPaths: &RepoPaths{