fix: use the correct cgroup policy to work on most of the systems

[alepane21]

We are using a policy that supports cgroup v2 with hybrid layout and cgroups v1.
But systems that only supports pure cgroup v2 will not be correctly working.
So I changed it to use the FromCgroup that is checking for V2, V2 Hybrid and also V1 systems.

Summary by CodeRabbit

• Refactor
  • Updated memory limit detection mechanism during initialization. The system's logging behavior for memory configuration remains unchanged, ensuring consistent operational transparency.

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Checklist

• I have discussed my proposed changes in an issue and have received approval to proceed.
• I have followed the coding standards of the project.
• Tests or benchmarks have been added or updated.
• Documentation has been updated on https://github.com/wundergraph/cosmo-docs.
• I have read the Contributors Guide.

[coderabbitai]

Walkthrough

Both plan_generator.go and supervisor_instance.go swap the memory limit provider from FromCgroupHybrid to FromCgroup during GOMEMLIMIT auto-configuration. The logging behavior for success and failure cases remains unchanged.

Changes

Cohort / File(s)	Summary
Memory limit provider update router/cmd/plan_generator.go, router/core/supervisor_instance.go	Replaces FromCgroupHybrid with FromCgroup when auto-configuring GOMEMLIMIT during initialization. Success and failure logging behavior unchanged.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10–15 minutes

• Memory limit provider is a direct, homogeneous replacement across two files with no control flow or error handling changes
• Verify that FromCgroup provides equivalent or improved behavior compared to FromCgroupHybrid in both environments (plan generation and supervisor initialization)

Pre-merge checks and finishing touches

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly summarizes the main change: replacing the cgroup policy from hybrid to the correct one to improve system compatibility.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

✨ Finishing touches

• 📝 Generate docstrings

---

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[github-actions]

Router image scan passed

✅ No security vulnerabilities found in image:

ghcr.io/wundergraph/cosmo/router:sha-dcb4c86b8b83f486bfab3eb042798db16582cb2c

[codecov]

Codecov Report

❌ Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.55%. Comparing base (8980fa8) to head (f8c3905).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
router/cmd/plan_generator.go	0.00%	1 Missing ⚠️
router/core/supervisor_instance.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2421      +/-   ##
==========================================
+ Coverage   60.75%   61.55%   +0.79%     
==========================================
  Files         229      229              
  Lines       23818    23814       -4     
==========================================
+ Hits        14470    14658     +188     
+ Misses       8101     7919     -182     
+ Partials     1247     1237      -10     

Files with missing lines	Coverage Δ
router/cmd/plan_generator.go	0.00% <0.00%> (ø)
router/core/supervisor_instance.go	0.00% <0.00%> (ø)

... and 20 files with indirect coverage changes

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