Implement Task 10 portable layout definition and launcher path portability

[RadDad87]

Summary

Implemented Task 10 with narrow packaging/readiness scope and Windows-local portability focus.

Files changed

• launch_z3r4h.bat
• README.md
• Z3R4H_CLEAN_ENV_CHECKLIST.md
• TASKS.md
• Z3R4H_PROGRESS_SUMMARY.md

What changed

• Updated launcher defaults to %~dp0-anchored relative paths:
  • PACKAGE_ROOT=%~dp0
  • LLAMA_SERVER_EXE=%PACKAGE_ROOT%runtime\llama.cpp\llama-server.exe
  • MODEL_PATH=%PACKAGE_ROOT%models\model.gguf
• Documented Open WebUI startup mode distinction:
  • external CLI in PATH (default)
  • optional bundled runtime command (example)
• Added portable package layout and runtime requirement documentation in README.
• Added portable layout preflight checks to clean-environment checklist.
• Updated Task/progress docs to reflect Task 10 completion.

Scope constraints honored

• No backend/product behavior changes beyond launcher path portability defaults.
• No dependencies added.
• No legal/license file edits.

Deferred beyond Task 10

• Installer generation/signing.
• CI/release automation.
• Bundled Open WebUI runtime build workflow.

Commit

• a21236ec

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Codex Task