Facts/os: avoid blank linux os.version on rolling releases

[asger-weirsoee]

INFO[1802] Starting user/group fetch                     logger=component.directory pid=999545 target=ak-sysd
DEBU[1802] dispatching event                             id=directory logger=sysd pid=999545 target=ak-sysd topic=sysd.directory.fetched
DEBU[1802] dispatching event                             logger=sysd pid=999545 target=ak-sysd topic=sysd.directory.fetched
INFO[1802] Finished user/group fetch                     logger=component.directory next=30m0s pid=999545 target=ak-sysd
DEBU[1829] Starting facts gathering...                   logger=component.device pid=999545 target=ak-sysd
DEBU[1829] Gathering...                                  area=disk logger=component.device pid=999545 target=ak-sysd
DEBU[1829] Gathering...                                  area=hardware logger=component.device pid=999545 target=ak-sysd
DEBU[1829] Gathering...                                  area=network logger=component.device pid=999545 target=ak-sysd
DEBU[1829] Gathering...                                  area=os logger=component.device pid=999545 target=ak-sysd
DEBU[1829] Gathering...                                  area=process logger=component.device pid=999545 target=ak-sysd
DEBU[1829] Gathering...                                  area=user logger=component.device pid=999545 target=ak-sysd
DEBU[1829] Gathering...                                  area=group logger=component.device pid=999545 target=ak-sysd
DEBU[1829] Gathering...                                  area=vendor logger=component.device pid=999545 target=ak-sysd
DEBU[1829] Finished facts gathering                      logger=component.device pid=999545 target=ak-sysd
WARN[1829] failed to checkin                             error="failed to checkin: HTTP Error '400 Bad Request' during request 'POST /api/v3/endpoints/agents/connectors/check_in/': \"{\"os\":{\"version\":[\"This field may not be blank.\"]}}\" (Request ID 'ec97fc27c5b34fafbaee4f123b6d1c34')" logger=component.device pid=999545 target=ak-sysd
DEBU[1831] Starting a new transaction [writable: false]  logger=storage.state
DEBU[1831] Starting a new transaction [writable: false] successfully  logger=storage.state

According to os-release(5)

PRETTY_NAME=

A pretty operating system name in a format suitable for presentation to the user. May or may not contain a release code name or OS version of some kind, as suitable. If not set, a default of "PRETTY_NAME="Linux"" may be used

So, version is not guaranteed to be present in PRETTY_NAME, and parsing a version from it can legitimately result in an empty value on rolling-release distributions.

This means that the entire check-in request is rejected because os.version is present but blank

The endpoint requires a value if version is sent, so the agent should either:

• send a valid version
• omit version entirely when no value can be derived, since the field i optional

[codecov]

Codecov Report

❌ Patch coverage is 71.15385% with 15 lines in your changes missing coverage. Please review.
✅ Project coverage is 38.08%. Comparing base (7d32797) to head (1a64312).

Files with missing lines	Patch %	Lines
pkg/platform/facts/os/os_linux.go	71.15%	11 Missing and 4 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #834       +/-   ##
===========================================
+ Coverage   16.58%   38.08%   +21.50%     
===========================================
  Files         204      203        -1     
  Lines        6827     6968      +141     
===========================================
+ Hits         1132     2654     +1522     
+ Misses       5553     3980     -1573     
- Partials      142      334      +192     

Flag	Coverage Δ
go-e2e	42.45% <72.72%> (?)
go-macos-15	13.47% <ø> (-0.37%)	⬇️
go-ubuntu-24.04	13.76% <72.72%> (+0.37%)	⬆️
go-ubuntu-24.04-arm	13.27% <71.15%> (+0.39%)	⬆️
go-windows-2025	12.76% <ø> (-0.36%)	⬇️

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