feat(agentapi): expose hidden parameter for coder_app

[zek]

Problem

The agentapi module creates a coder_app resource for the web chat UI, but does not expose the hidden attribute from the coder_app resource. This means users cannot hide the AgentAPI web app from the Coder dashboard.

The coder_app resource supports hidden = true since Coder v2.16, but neither the agentapi nor the claude-code module passes this through.

Use Case

I use Claude Code exclusively via terminal (SSH / code-server). The AgentAPI web chat UI is not useful for my workflow, but I still want coder_ai_task to work (Tasks feature requires the app to exist).

Setting hidden = true would keep the app functional (healthchecks, task status reporting) while hiding it from the dashboard UI.

Proposed Change

In registry/coder/modules/agentapi/main.tf:

Add a variable:

variable "web_app_hidden" {
  type        = bool
  description = "Whether to hide the web app from the dashboard UI."
  default     = false
}

Add to the coder_app.agentapi_web resource:

hidden = var.web_app_hidden

In registry/coder/modules/claude-code/main.tf:

Add a variable:

variable "web_app_hidden" {
  type        = bool
  description = "Whether to hide the web app from the dashboard UI."
  default     = false
}

Pass it to the agentapi module:

module "agentapi" {
  # ...existing params...
  web_app_hidden = var.web_app_hidden
}

This is a backward-compatible, non-breaking change (defaults to false).