feat(matifali): add Omnigent Docker template

[matifali]

Summary

Adds an Omnigent Docker template under the personal matifali namespace, combining Omnigent, Claude Code, Codex, Coder AI Gateway, and a shallow clone of github.com/coder/coder.

This was extracted from #925 so the reusable Omnigent module and the opinionated Docker template can be reviewed independently.

Changes

• Add the template under registry/matifali/templates/omnigent-docker.
• Add the matifali contributor profile and link the hosted Omnigent module and Docker template.
• Configure Claude Code and Codex through Coder AI Gateway.
• Use compatible module constraints so minor and patch releases are selected automatically.
• Install shared dependencies required by the AI tools on the Ubuntu-based image.
• Coordinate repository cloning, AI tool setup, and Omnigent startup with coder exp sync.
• Add the Omnigent registry icon.

Validation

• terraform fmt -check -recursive registry/matifali/templates/omnigent-docker
• Imported the exact PR template as Coder template version e77335c8-2899-449e-8fb6-fa7e4c516b99.
• Terraform initialized and planned successfully, resolving:
  • matifali/omnigent 0.0.1
  • coder/git-clone 2.0.2
  • coder/claude-code 5.2.0
  • coder-labs/codex 5.3.0
• Created workspace test-omnigent-docker-pr-1022 from the imported template.
• Workspace build chore: add CI step for validating contributor READMEs #1 succeeded with 16 resources created and reached ready.
• Verified:
  • Omnigent app health is healthy.
  • GET /health returns { "status": "ok" }.
  • The Coder repository was cloned successfully.
  • Claude Code 2.1.215, Codex CLI 0.144.6, and Omnigent 0.5.1 are installed.
  • Omnigent server and host processes are running.
  • The Omnigent host is connected to the local server.
  • All startup scripts completed successfully.

Continuation of #925

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