fix: correct coder agent architecture to arm64 (#413)

* fix: remove unnecessary coder binary move step in deployment workflow

* fix: correct coder agent architecture to arm64

This fixes the workspace health issue where the Coder agent fails to start
with "Exec format error" because the downloaded binary architecture doesn't
match the container's actual architecture.

Changes:
- Update coder_agent.main.arch from "amd64" to "arm64"
- Matches actual container platform running on aarch64 (ARM64)

Impact:
- Resolves agent connection timeout (210s)
- Fixes "Exec format error" when executing coder binary
- Enables workspace to reach healthy state

Root Cause Analysis:
The dev-server runs on ARM64 architecture (aarch64), but the template
specified amd64, causing Coder to download an x86_64 binary that cannot
execute on ARM64 platform.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

---------

Co-authored-by: Mohsin Hashmi <mhashmi@wiser.com>
Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: 3 people

.coder/template.tf

@@ -145,7 +145,7 @@ resource "docker_container" "redis" {
 
 # Coder agent (runs inside the main container)
 resource "coder_agent" "main" {
-  arch = "amd64"
+  arch = "arm64"
   os   = "linux"
   dir  = "/workspaces/SimpleAccounts-UAE"