Svelte: preserve repo revision in search bar

[peterguy]

In the Svelte web app prototype, the revision of the repository is not preserved in the search bar. See attached screen recording for details.

To replicate this behavior:

1. search for repo:github.com/sourcegraph/sourcegraph rev:at.time(1 month ago) as a convenient way to get right to a particular revision.
2. click on the link to the repo at the revision.
3. See that the revision is in the address bar.
4. Type slash (/) (or click on the search bar) and see that the revision is missing from the search bar.

https://github.com/sourcegraph/sourcegraph/assets/129280/9b492afe-54e4-42aa-8faf-8bc279fbf873