[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

```

在 macOS 上重现第一次 workspace 分配，并检查 ~/Library/Application Support/Herd/config/valet/Nginx/silver-lobster.test，尤其是 issue 中报告的格式错误的 rewrite 和占位符值。使用 nginx 验证生成的 vhost，并确认 Herd 的 .test 域名仍可访问，同时 Polyscope workspace 正常工作。

由索引模型根据 Issue 内容生成。