Root cause

skillserver versions <name> for a skill that isn't on the server crashed with an unhandled HttpRequestException on the server's 404 (Aborted (core dumped), exit 134), dumping a stack trace.

VersionsCommand.ExecuteAsync calls client.GetSkillVersionsAsync(name), which uses GetFromJsonAsync. That helper calls EnsureSuccessStatusCode() internally and throws HttpRequestException on a 404. Nothing caught it, so the process aborted. Sibling read commands (verify, download-subagent) already wrap their calls in a try/catch (HttpRequestException); versions was the outlier.

Fix

Catch HttpRequestException in VersionsCommand, matching the sibling pattern:

• A 404 prints a clean Skill '<name>' not found. and exits 1.
• Any other HttpRequestException falls through to ConsoleOutput.HandleHttpError, exiting 1.

The fix is scoped to the versions path. SkillServerClient is unchanged, so verify and download-subagent are unaffected.

Added VersionsCommandTests with two cases using the existing mock-HttpMessageHandler pattern: a 404 returns 1 without throwing (regression test for this bug), and a successful response returns 0 and lists versions.

Verification

Built the CLI from this branch and ran it against a real ghcr.io/netclaw-dev/skillserver:0.4.0 server.

Missing skill — now exits 1 with a readable message, no stack trace / no core dump:

$ skillserver versions no-such-skill
Skill 'no-such-skill' not found.
exit=1

Existing skill — still lists versions correctly (exit 0):

$ skillserver publish .../hello-greeter
Published [email protected]

$ skillserver versions hello-greeter
VERSION  PUBLISHED   LATEST  SHA256
1.0.0    2026-07-22  *       sha256:37e4bb27...
exit=0

Sibling commands still behave (exit 1, no crash) — client untouched, no regression:

$ skillserver verify .../k8s-log-triage        # not published to server
Error: Response status code does not indicate success: 404 (Not Found).
exit=1

$ skillserver download-subagent no-such-agent 1.0.0 out.md
Error: Response status code does not indicate success: 404 (Not Found).
exit=1

dotnet build (Release): 0 warnings, 0 errors. dotnet test (CLI test project): 114 passed, 0 failed.

Closes #142