cmd: cleanup

[pinebit]

To reduce the scope of the other (DKG) PR, this work just cleans up the cmd package:

• removed view-cluster-manifest command that is unused,
• removed t.Parallel() as we don't allow it anywhere else,
• disabled one flakey test that is less important vs build stability
• other minor improvements

category: refactor
ticket: none

[sonarqubecloud]

Quality Gate failed

Failed conditions
26.7% Duplication on New Code (required ≤ 15%)

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

❌ Patch coverage is 84.61538% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 53.65%. Comparing base (41ae91c) to head (d27481c).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
cmd/exit_delete.go	50.00%	1 Missing ⚠️
cmd/exit_fetch.go	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3990      +/-   ##
==========================================
- Coverage   55.07%   53.65%   -1.43%     
==========================================
  Files         225      224       -1     
  Lines       37264    37172      -92     
==========================================
- Hits        20524    19943     -581     
- Misses      14565    15109     +544     
+ Partials     2175     2120      -55     

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