feat(open-collaboration-tools): add OCT module

[Edd88-pixel]

Description

Adds an Open Collaboration Tools module for configuring the official OCT extension in Coder web IDEs.

The module exposes composable extension and settings outputs for code-server and VS Code Web while keeping the long-lived OCT server and OAuth credentials outside individual workspaces.

Why

Coder workspaces need a reusable way to configure the OCT extension without coupling workspace lifecycle to the shared collaboration server or storing OAuth credentials in Terraform state.

Changes

• add composable extensions and settings outputs for code-server and VS Code Web;
• validate HTTPS server URLs, with HTTP limited to local development;
• support prompt, allowlist, and automatic join policies plus preinstalled extensions;
• document OAuth2/PKCE setup, restricted-network operation, session commands, and OCT health routes;
• add Terraform and TypeScript coverage plus two screenshots from the two-workspace E2E flow.

Type of Change

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

Module Information

Path: registry/edd88-pixel/modules/open-collaboration-tools
New version: v1.0.0
Breaking change: [ ] Yes [x] No

Testing & Validation

• Tests pass (bun test)
• Code formatted (bun fmt)
• Changes tested locally

Validation

• terraform validate — passed
• terraform test -verbose — 11 passed, 0 failed
• bun test registry/edd88-pixel/modules/open-collaboration-tools — 5 passed, 0 failed
• targeted Prettier and terraform fmt -check — passed
• go run ./cmd/readmevalidation with Go 1.25 — passed
• two-user Coder E2E with OAuth2/PKCE, join rejection and approval, participant presence, remote cursor, and bidirectional editing — passed

Related Issues

Closes #1032