discovery: use interface CIDR for auto-generated subnet, tests

[BeryJu]

No description provided.

[netlify]

✅ Deploy Preview for beryju-gravity canceled.

Name	Link
🔨 Latest commit	bdece29
🔍 Latest deploy log	https://app.netlify.com/sites/beryju-gravity/deploys/678c321e5c3dee00080703f0

[codecov]

Bundle Report

Changes will increase total bundle size by 392 bytes (0.01%) ⬆️. This is within the configured threshold ✅

Detailed changes

Bundle name	Size	Change
gravity-ui-esm	3.71MB	392 bytes (0.01%) ⬆️

[codecov]

Codecov Report

Attention: Patch coverage is 53.12500% with 15 lines in your changes missing coverage. Please review.

Project coverage is 69.72%. Comparing base (760b3e0) to head (bdece29).
Report is 1 commits behind head on main.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
pkg/roles/discovery/role.go	59.09%	6 Missing and 3 partials ⚠️
pkg/roles/discovery/api_subnets.go	40.00%	2 Missing and 1 partial ⚠️
pkg/roles/discovery/subnet.go	33.33%	1 Missing and 1 partial ⚠️
pkg/extconfig/ip.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1452      +/-   ##
==========================================
+ Coverage   69.60%   69.72%   +0.12%     
==========================================
  Files         144      144              
  Lines        8031     8053      +22     
==========================================
+ Hits         5590     5615      +25     
+ Misses       1953     1946       -7     
- Partials      488      492       +4     

Flag	Coverage Δ
e2e	42.13% <53.12%> (+0.47%)	⬆️
unittest	59.47% <3.12%> (-0.99%)	⬇️

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