Summary: URL is double encoded in classic, but should not be when opening blue ocean.

There is no ATH coverage for "open blue ocean" (should there be?)

404 should be another ticket (likely already is one open).

Steps to reproduce

1. Go to https://ci.blueocean.io/job/blueocean/job/bug%252FJENKINS-39158/1/
2. Click open in blue ocean
3. No 404, the page is broken
4. URL is https://ci.blueocean.io/blue/organizations/jenkins/blueocean/detail/bug%252FJENKINS-39158/1/

What should happen
The real URL to this run is https://ci.blueocean.io/blue/organizations/jenkins/blueocean/detail/bug%2FJENKINS-39158/1/pipeline

Why is the 404 handling broken? (A: should be in another ticket, not related to this)
Where is the ATH for this? (A: isn't a regression, no coverage for open button yet - but may as well should be)