fix(zed): fix settings JSON parsing with base64 encoding

[matifali]

Problem

The Zed module's settings parsing was broken. The previous implementation used quote escaping:

SETTINGS_JSON='${replace(var.settings, "\"", "\\\"")}'

This produced invalid JSON like {\"theme\":\"dark\"} which jq could not parse because the backslash-escaped quotes are not valid JSON syntax.

Solution

Changed to use base64 encoding internally:

locals {
  settings_b64 = var.settings != "" ? base64encode(var.settings) : ""
}

# In the script:
SETTINGS_B64='${local.settings_b64}'
SETTINGS_JSON="$(echo -n "${SETTINGS_B64}" | base64 -d)"

User interface remains the same - users still provide plain JSON via jsonencode() or heredoc:

module "zed" {
  source   = "..."
  agent_id = coder_agent.main.id
  settings = jsonencode({
    theme    = "dark"
    fontSize = 14
  })
}

Testing

Added comprehensive tests:

Terraform tests (5):

• URL generation (default, folder, agent_name)
• Settings base64 encoding verification
• Empty settings edge case

Container e2e tests (3):

• Creates settings file with correct JSON (including special chars: quotes, backslashes, URLs)
• Merges with existing settings via jq
• Exits early with empty settings

Also fixed existing tests to use override_data for proper workspace mocking.