feat: Add shell login options from /etc/shells

[arran4]

Closes #3
This PR introduces the functionality to dynamically discover shell login options by parsing /etc/shells or any customized file specified by session.ShellsFile. Shells are validated using ExecLookPath and added to the list of available sessions with the type C.

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PR created automatically by Jules for task 16853790196739824059 started by @arran4

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[gemini-code-assist]

Code Review

This pull request implements dynamic discovery of shell login sessions by parsing the system's shells file (typically /etc/shells). It introduces a new discovery method, integrates it into the main session discovery logic, and adds comprehensive unit tests. Review feedback suggests removing the development plan file from the repository and improving the robustness of the shell file parser by using strings.Fields to better handle trailing comments and whitespace.

[gemini-code-assist]

This file appears to be a development plan or internal notes and should not be included in the final repository. Please remove it before merging.

[arran4]

This file appears to be a development plan or internal notes and should not be included in the final repository. Please remove it before merging.

@jules

[gemini-code-assist]

The current parsing of /etc/shells is sensitive to trailing comments or extra whitespace. Using strings.Fields to extract the first token is more robust and aligns better with how system utilities typically parse this file.

		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue
		}

		// Use only the first field to ignore trailing comments/whitespace
		fields := strings.Fields(line)
		if len(fields) == 0 {
			continue
		}
		shellPath := fields[0]

		// Attempt to resolve the shell binary
		if _, err := d.ExecLookPath(shellPath); err != nil {
			continue // Skip invalid shells
		}

		name := filepath.Base(shellPath)

		sessions = append(sessions, Session{
			Name: name,
			Exec: shellPath,
			Type: "C",
			Path: ShellsFile,
		})

[arran4]

The current parsing of /etc/shells is sensitive to trailing comments or extra whitespace. Using strings.Fields to extract the first token is more robust and aligns better with how system utilities typically parse this file.

  line := strings.TrimSpace(scanner.Text())
  if line == "" || strings.HasPrefix(line, "#") {
  	continue
  }

  // Use only the first field to ignore trailing comments/whitespace
  fields := strings.Fields(line)
  if len(fields) == 0 {
  	continue
  }
  shellPath := fields[0]

  // Attempt to resolve the shell binary
  if _, err := d.ExecLookPath(shellPath); err != nil {
  	continue // Skip invalid shells
  }

  name := filepath.Base(shellPath)

  sessions = append(sessions, Session{
  	Name: name,
  	Exec: shellPath,
  	Type: "C",
  	Path: ShellsFile,
  })

@jules or use github.com/arran4/go-consume