feat: slogging in agent

[AustinAbro321]

Description

This changes the Zarf agent to use slog style logging

Related Issue

Fixes #3188

Checklist before merging

• Test, docs, adr added or updated as needed
• Contributor Guide Steps followed

[netlify]

✅ Deploy Preview for zarf-docs canceled.

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🔍 Latest deploy log	https://app.netlify.com/sites/zarf-docs/deploys/672a70c0567984000809f232

[codecov]

Codecov Report

Attention: Patch coverage is 73.68421% with 15 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/internal/agent/start.go	0.00%	8 Missing ⚠️
src/internal/agent/http/proxy.go	0.00%	4 Missing ⚠️
src/internal/agent/http/admission/handler.go	57.14%	3 Missing ⚠️

Files with missing lines	Coverage Δ
src/internal/agent/hooks/argocd-application.go	76.05% <100.00%> (+1.42%)	⬆️
src/internal/agent/hooks/argocd-repository.go	76.92% <100.00%> (+1.11%)	⬆️
src/internal/agent/hooks/flux-gitrepo.go	85.93% <100.00%> (+1.45%)	⬆️
src/internal/agent/hooks/flux-helmrepo.go	77.27% <100.00%> (+1.08%)	⬆️
src/internal/agent/hooks/flux-ocirepo.go	82.55% <100.00%> (+0.63%)	⬆️
src/internal/agent/hooks/pods.go	73.75% <100.00%> (+1.38%)	⬆️
src/internal/agent/http/admission/handler.go	58.53% <57.14%> (+0.51%)	⬆️
src/internal/agent/http/proxy.go	38.39% <0.00%> (-0.35%)	⬇️
src/internal/agent/start.go	0.00% <0.00%> (ø)

... and 2 files with indirect coverage changes

[mkcp]

LGTM