Add nurl and vainstr CLI tools (v0.39.0)

- Add nurl: NIP-98 authenticated HTTP client for testing owner APIs
- Add vainstr: vanity npub generator using fast secp256k1 library
- Update CLAUDE.md with documentation for both tools
- Properly handle secp256k1 library loading via p8k.New()

Files modified:
- cmd/nurl/main.go: New NIP-98 HTTP client tool
- cmd/vainstr/main.go: New vanity npub generator
- CLAUDE.md: Added usage documentation for nurl and vainstr
- go.mod/go.sum: Added go-arg dependency for vainstr
- pkg/version/version: Bump to v0.39.0

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

go.sum

@@ -6,6 +6,10 @@ github.com/ImVexed/fasturl v0.0.0-20230304231329-4e41488060f3 h1:ClzzXMDDuUbWfNN
 github.com/ImVexed/fasturl v0.0.0-20230304231329-4e41488060f3/go.mod h1:we0YA5CsBbH5+/NUzC/AlMmxaDtWlXeNsqrwXjTzmzA=
 github.com/adrg/xdg v0.5.3 h1:xRnxJXne7+oWDatRhR1JLnvuccuIeCoBu2rtuLqQB78=
 github.com/adrg/xdg v0.5.3/go.mod h1:nlTsY+NNiCBGCK2tpm09vRqfVzrc2fLmXGpBLF0zlTQ=
+github.com/alexflint/go-arg v1.6.1 h1:uZogJ6VDBjcuosydKgvYYRhh9sRCusjOvoOLZopBlnA=
+github.com/alexflint/go-arg v1.6.1/go.mod h1:nQ0LFYftLJ6njcaee0sU+G0iS2+2XJQfA8I062D0LGc=
+github.com/alexflint/go-scalar v1.2.0 h1:WR7JPKkeNpnYIOfHRa7ivM21aWAdHD0gEWHCx+WQBRw=
+github.com/alexflint/go-scalar v1.2.0/go.mod h1:LoFvNMqS1CPrMVltza4LvnGKhaSpc3oyLEBUZVhhS2o=
 github.com/aperturerobotics/go-indexeddb v0.2.3 h1:DfquIk9YEZjWD/lJyBWZWGCtRga43/a96bx0Ulv9VhQ=
 github.com/aperturerobotics/go-indexeddb v0.2.3/go.mod h1:JV1XngOCCui7zrMSyRz+Wvz00nUSfotRKZqJzWpl5fQ=
 github.com/btcsuite/btcd/btcec/v2 v2.3.4 h1:3EJjcN70HCu/mwqlUsGK8GcNVyLVxFDlWurTXGPFfiQ=
@@ -126,6 +130,7 @@ github.com/sosodev/duration v1.3.1/go.mod h1:RQIBBX0+fMLc/D9+Jb/fwvVmo0eZvDDEERA
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
+github.com/stretchr/testify v1.2.2/go.mod h1:a8OnRcib4nhh0OaRAV+Yts87kKdq0PP7pXfy6kDkUVs=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=