fix(doctor): remove circular error message in --fix mode

When `bd doctor --fix` fails to apply a fix, it was showing
"Manual fix: Run 'bd doctor --fix' ..." which is circular and unhelpful.

Now extracts just the manual command from the fix message:
- "..., or manually: <cmd>" -> extracts <cmd>
- "bd doctor --fix or <alt>" -> extracts <alt>
- No alternative available -> shows nothing

Closes GH#403

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

cmd/bd/doctor_test.go

@@ -1265,3 +1265,62 @@ func TestCheckSyncBranchHookQuick(t *testing.T) {
 		})
 	}
 }
+
+// TestExtractManualFix tests the extractManualFix function (GH#403)
+func TestExtractManualFix(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:     "manually pattern with git config",
+			input:    "Run 'bd doctor --fix' to update to correct config, or manually: git config merge.beads.driver \"bd merge %A %O %A %B\"",
+			expected: "git config merge.beads.driver \"bd merge %A %O %A %B\"",
+		},
+		{
+			name:     "manually pattern with newline",
+			input:    "Run 'bd doctor --fix' to auto-migrate, or manually:\nbd init && bd import",
+			expected: "bd init && bd import",
+		},
+		{
+			name:     "or alternative after bd doctor --fix",
+			input:    "Run 'bd doctor --fix' or bd init",
+			expected: "bd init",
+		},
+		{
+			name:     "or alternative before bd doctor --fix",
+			input:    "Run: bd init (safe to re-run) or bd doctor --fix",
+			expected: "bd init (safe to re-run)",
+		},
+		{
+			name:     "just bd doctor --fix",
+			input:    "Run 'bd doctor --fix'",
+			expected: "",
+		},
+		{
+			name:     "no bd doctor --fix at all",
+			input:    "Run 'bd init' to initialize the database",
+			expected: "Run 'bd init' to initialize the database",
+		},
+		{
+			name:     "empty input",
+			input:    "",
+			expected: "",
+		},
+		{
+			name:     "update configuration suggestion",
+			input:    "Run 'bd doctor --fix' to update the configuration",
+			expected: "",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			result := extractManualFix(tc.input)
+			if result != tc.expected {
+				t.Errorf("extractManualFix(%q) = %q, expected %q", tc.input, result, tc.expected)
+			}
+		})
+	}
+}