Add support for new mandatory template build parameters

[fioan89]

I was in the middle of some testing and had a workspace that was still using an outdated template. When I tried to run Update and Start from the Coder Toolbox, I got a very generic error. After some investigation, I realized the template now includes new mandatory parameters that need to be configured.

In the web dashboard, this situation is handled much more gracefully—it shows a pop-up and guides you directly to the workspace parameter configuration. We should implement something similar in the Toolbox.

3.1.0.61894 64678 2025-12-05 23:05:48.113 INFO  :[//dev.coder.com/](https://codercom.slack.com//dev.coder.com/)... LoggingInterceptor             Plugin com.coder.toolbox > request --> POST https://dev.coder.com/api/v2/workspaces/9c372612-88ff-435e-9836-2be25e41091c/builds
Coder-Session-Token: <redacted>
User-Agent: Coder Toolbox/0.8.0 (MAC; ARM64)
{"template_version_id":"287bb624-8e0f-451c-81cc-c0b713cff090","transition":"start"}

3.1.0.61894 64678 2025-12-05 23:05:48.624 INFO  :[//dev.coder.com/](https://codercom.slack.com//dev.coder.com/)... LoggingInterceptor             Plugin com.coder.toolbox > response <-- 400  https://dev.coder.com/api/v2/workspaces/9c372612-88ff-435e-9836-2be25e41091c/builds
content-type: application/json; charset=utf-8
set-cookie: csrf_token=CBSpZdc429hEqe94CmB5IB2flujiKl6cPkPDVlL0yNQ=; Path=/; HttpOnly; SameSite=Lax
traceparent: 00-0a58e0e27d303880f1cfbbee0c1489d6-193452fcfcfef028-01
vary: Origin
vary: Cookie
x-coder-build-version: v2.29.0-devel+61beb7bfa
x-coder-request-id: bc45973e-3510-486d-a5a6-0cd09f71d0a7
x-content-type-options: nosniff
x-ratelimit-limit: 512
x-ratelimit-remaining: 511
x-ratelimit-reset: 1764968760
x-span-id: 193452fcfcfef028
x-trace-id: 0a58e0e27d303880f1cfbbee0c1489d6
content-length: 267
date: Fri, 05 Dec 2025 21:05:48 GMT
{"message":"Unable to validate parameters","validations":[{"field":"Select IDEs","detail":"Values must be a valid option; Value \"[\\\"vscode\\\",\\\"code-server\\\",\\\"cursor\\\",\\\"mux\\\"]\" is not a valid option, values \"mux\" are missing from the options"}]}