refactor(cli): inline project label helper

[upsetbit]

Closes #92.

Summary

• move CLI project-label normalization into internal/cli/render
• remove the one-package internal/projectlabel helper
• keep the previous normalization and fallback coverage next to the renderer

Local validation

• go test ./internal/cli/render ./internal/cli/... -race
• devbox run -- just lint
• devbox run -- just test-race

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