Handle SSH commands on servers without a home directory

[GT-610]

Summary

• Add SSHExecResult with exit code, stdout, stderr, and success status.
• Treat stderr warnings as non-fatal when the remote command succeeds.
• Improve script installation error reporting and retry tracking.
• Add coverage for SSH command result handling.

Testing

• Added unit tests for successful, failed, and missing-exit-code SSH results.

Resolve #1240

Summary by CodeRabbit

• New Features

  • Added clearer SSH command results, including exit codes, standard output, and error output.
  • Improved success detection for remote commands, including commands that complete without an explicit exit code.

• Bug Fixes

  • Improved installation failure messages by reporting the most relevant command output.
  • Improved server error handling and retry tracking when script installation fails.

• Tests

  • Added coverage for successful, failed, and indeterminate SSH command outcomes.

[coderabbitai]

📝 Walkthrough

Walkthrough

SSH command execution now returns an SSHExecResult containing exit code, stdout, and stderr, with success determined by exit status or stderr when no exit code is available. Server script installation handling consumes the structured result, formats failures, and updates retry tracking. Tests cover the success behavior for zero, non-zero, and null exit codes.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title is relevant to the PR’s SSH command handling changes, especially the server-side fallback for script execution on nonstandard environments.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/issue-1240-missing-home

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