feat(coder-utils): nest scripts under module_directory/scripts

[matifali]

Summary

Move script files from the flat ${module_directory} to a scripts/ subdirectory, and prefix each script's filename with ${agent_name}-utils- so multiple coder-utils instances can safely share a module_directory. Mirrors the layout #870 established for logs/ and aligns with the Module Data Layout standard in AGENTS.md (#869).

Changes

• Compute local.scripts_directory = "${var.module_directory}/scripts" and use it for every *.sh path.
• Script filenames are now ${agent_name}-utils-{pre_install,install,post_install,start}.sh so two coder-utils instances don't collide on disk.
• Pre-install and install coder_scripts mkdir -p the scripts/ sub-path before writing their .sh; post-install and start sync-depend on install, so the directory already exists by the time they run.
• Update the module_directory description to call out the nested scripts/ and logs/ paths.
• Add test_scripts_nested_under_module_directory asserting the new paths (including the ${agent_name}-utils- prefix) and the mkdir -p in each script.
• README: add a "Script file locations" section documenting the new layout.
• Bump module version to v1.3.0.

Breaking Changes

Consumers reading ${module_directory}/install.sh (and friends) directly must look under ${module_directory}/scripts/${agent_name}-utils-install.sh instead. No in-repo consumers exist today.

Validation

• terraform fmt -recursive clean
• terraform validate clean
• terraform test → 16/16 pass (includes the new test_scripts_nested_under_module_directory)
• bun test main.test.ts → 5/5 pass
• prettier --check clean

🤖 This PR was created with the help of Coder Agents, and needs a human review. 🧑‍💻

[35C4n0r]

LGTM