style: run gofmt on lint-failing files

[marcus]

Summary

• run gofmt -w on the Go files currently reported by gofmt -l .
• keep the scope to formatting cleanup and remove the accidental smart-quote comment regression from the previous attempt
• add a small test helper in internal/features/features_test.go so feature-flag tests reset relevant TD_* env vars and pass under the current shell environment

Validation

• gofmt -l .
• go vet ./...
• go test ./...
• go build ./...

Notes

• Assumption: this pass does not introduce a new lint tool; gofmt remains the active quality bar called out in the repo README.
• Unrelated untracked files already present in the worktree were left untouched.

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Automated by nightshift