[Bug]: Polyscope breaks herd nginx file when generating a workspace

### Platform

macOS

### Operating system version

macos 15.6

### System architecture

ARM64 (M1, M2, etc)

### PolyScope Version

latest

### Bug description

All of herds .test domains refused to connect after opening polyscope for the first time and assigning it to a Sites/Repo on my mac. claude helped me track the root cause to a malformed vhost written by polyscope.

~/Library/Application\ Support/Herd/config/valet/Nginx/silver-lobster.test

1 server {
2 listen 127.0.0.1:80;
3 #listen 127.0.0.1:80; # valet loopback
4 server_name silver-lobster.test www.silver-lobster.test *.silver-lobster.test;
5 return 301 httpspasted10:36 AMClaude responded: Confirmed — line 27 rewrite ^ "" last; (and line 70).Identified broken placeholder configuration and prescribed remedial stepsIdentified broken placeholder configuration and prescribed remedial stepsConfirmed — line 27 rewrite ^ "" last; (and line 70). nginx 1.25.4 rejects the empty "" replacement, and that's fatal for the whole config. This whole file is a Polyscope placeholder vhost — root /, fastcgi_index "", SCRIPT_FILENAME "", the blank rewrite — it's a skeleton for a workspace that never got a real document root wired in. Broken as written, and it's been taking all of Herd down with it.

I fixed it by removing the file
mv ~/Library/Application\ Support/Herd/config/valet/Nginx/silver-lobster.test

However that gets herd working but not polyscope. I'm unsure why its causing a malformed vhost?

### Steps to reproduce

_No response_

### Relevant log output

```shell

```

Reproduce the first workspace assignment on macOS and inspect ~/Library/Application Support/Herd/config/valet/Nginx/silver-lobster.test, especially the malformed rewrite and placeholder values reported in the issue. Validate the generated vhost with nginx and confirm that Herd .test domains remain reachable while the Polyscope workspace works.

Written by the indexing model from the issue text.