docs: Add comprehensive SLO Agent and Risk Gate Wizard guides

[btotharye]

• Add SLO Agent guide covering service types, CLI usage, code pattern detection, targets, integration, and Python API
• Add Risk Gate Wizard guide with step-by-step walkthroughs, gate templates, file patterns, severity thresholds, and examples
• Update mkdocs.yml navigation to include both new guides in the Guides section
• Both guides are production-ready with best practices and troubleshooting sections

Description

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Documentation update
• Content pack addition/update
• CI/CD or tooling change

Changes Made

Testing

• Tests pass locally (make test)
• Linting passes (make lint)
• Formatting is correct (make format-check)
• Tested manually with:

Related Issues

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings or errors
• I have added tests that prove my fix is effective or that my feature works
• New and existing tests pass locally with my changes

Additional Notes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.93%. Comparing base (d47c9b6) to head (70621df).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #52   +/-   ##
=======================================
  Coverage   92.93%   92.93%           
=======================================
  Files          29       29           
  Lines        3129     3129           
=======================================
  Hits         2908     2908           
  Misses        221      221           

Flag	Coverage Δ
unittests	92.93% <ø> (ø)

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