Add dynamic completion for profile and auth refs

[rmanibus]

Summary

• add a hidden completion query path for dynamic candidates
• use it to complete -profile and -auth-ref from the active profiles file across bash, zsh, and fish
• add coverage for candidate resolution and emitted completion scripts

Testing

• go test -count=1 ./cmd/cloudstic -run 'TestCompletion|TestRunCompletionQuery'

[codecov]

Codecov Report

❌ Patch coverage is 81.96721% with 22 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
cmd/cloudstic/completion_dynamic.go	73.68%	12 Missing and 8 partials ⚠️
cmd/cloudstic/main.go	0.00%	2 Missing ⚠️

📢 Thoughts on this report? Let us know!