Push skills unsigned until keyless signing lands

[samuv]

Summary

• The skills build/publish workflow has been failing on every push-enabled run since the skill-push signing requirement landed: pushing now requires either --key or --no-sign, and this workflow passed neither, so every push errors with signing key required.
• Keyless push signing (Keyless OIDC push signing for thv skill push #6307) is in progress but not yet shipped (gated on a toolhive-core release), so as an interim fix, pass --no-sign to both thv skill push invocations to unblock CI. A TODO(#6307) marks where to switch to real signing once it lands.

Type of change

• Bug fix (non-breaking change which fixes an issue)

Test plan

• Reviewed the workflow diff manually; change is scoped to adding --no-sign to the two existing thv skill push calls, no other behavior changes.

Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 72.92%. Comparing base (8f294e2) to head (7b5d36f).

Additional details and impacted files

@@ Coverage Diff @@## main #6334 +/- ##
==========================================
- Coverage 72.96% 72.92% -0.05% 
==========================================
Files 742 742 Lines 78236 78236 ==========================================
- Hits 57088 57053 -35 - Misses 17168 17201 +33 - Partials 3980 3982 +2 

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