refactor: simplification

[rustatian]

Reason for This PR

Remove duplicate worker command setup.

Description of Changes

• Use one command factory for standalone workers and pools. Remove the duplicate factory and its cached command state.
• Pass optional command arguments directly to exec.CommandContext for workers and startup commands.

License Acceptance

By submitting this pull request, I confirm that my contribution is made under the terms of the MIT license.

PR Checklist

• All commits in this PR are signed (git commit -s).
• The reason for this PR is clearly provided (issue no. or explanation).
• The description of changes is clear and encompassing.
• Any required documentation changes (code and docs) are included in this PR.
• Any user-facing changes are mentioned in CHANGELOG.md.
• All added/changed functionality is tested.

[Copilot]

Copilot review overview

🟢 Approval recommended

The refactor preserves existing behavior while removing redundant command setup.

Review effort: Balanced
Findings: None

What changed in this PR

Simplifies worker and startup command creation by consolidating command factories and removing redundant state.

Changes:

• Uses customCmd for standalone workers and pools.
• Removes cached command arguments and duplicate factory types.
• Passes optional arguments directly to exec.CommandContext.

File	Description
plugin.go	Unifies worker and pool command creation.
internal.go	Consolidates command factories and simplifies argument handling.
init.go	Simplifies startup command and environment construction.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.45%. Comparing base (214a12b) to head (d45fe96).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #160      +/-   ##
==========================================
+ Coverage   90.00%   92.45%   +2.45%     
==========================================
  Files           4        4              
  Lines         180      159      -21     
==========================================
- Hits          162      147      -15     
+ Misses         18       12       -6     

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