fix(code-server): coordinate extension recommendations

[Edd88-pixel]

Why

auto_install_extensions reads workspace recommendations only once. When a repository is cloned by another startup script, code-server can check before .vscode/extensions.json exists and silently skip the recommended extensions.

Coder startup coordination now provides a deterministic way to wait for the clone instead of polling for a fixed duration.

Changes

• Add a pre_auto_install_extensions_script hook that runs immediately before workspace recommendations are read.
• Propagate hook failures instead of continuing with a partial startup.
• bump the documented module version to 1.6.0.

Validation

• `bun test registry/coder/modules/code-server/main.test.ts — passed.
• terraform test for the code-server module — 8 passed, 0 failed.
• terraform validate, Terraform format check, Prettier, ShellCheck, and README validation — passed.
• Real Coder v2.33.11 E2E

Type of Change

• New module
• New template
• Bug fix
• Feature/enhancement
• Documentation
• Other

Module Information

Path: registry/coder/modules/code-server
New version: v1.6.0
Breaking change: [ ] Yes [x] No

Related Issues

Closes #57

[Edd88-pixel]

@35C4n0r can you review ?