fix(eos_ai): LLMClient URL normalization, env var support, and unit test suite

[iamsayanmandal]

Summary

Three related fixes that make the AI/LLM subsystem production-ready and restore a green CI gate on master.

1. LLMClient URL bugs — _call_openai_compat appended /v1/chat/completions unconditionally, causing /v1/v1/chat/completions when OPENAI_BASE_URL already contains /v1. Bare Ollama hosts without http:// crashed urllib. Empty api_key sent a stray Authorization: Bearer header that local servers (vLLM, llama.cpp) reject. Empty choices list returned success=True silently.

2. LLMClient has zero unit tests — added the first-ever test suite (35 tests, fully offline with mocks).

3. CI lint gate broken — ruff check . failed on 4 findings before running any test. Also added missing PackageRecipe.to_dict() which caused ebuild update-index to crash.

Type of Change

• \feat — New feature
• \fix — Bug fix
• docs — Documentation only
• style — Formatting, no code change
• \refactor — Code restructuring without behavior change
• \test — Add or fix tests
• \build — Build system or dependency changes
• ci — CI/CD pipeline changes
• perf — Performance improvement

Changes

• Add _normalize_openai_url(): strips trailing slash, detects existing /v1, appends correct suffix — prevents /v1/v1/chat/completions double-path
• Add _ensure_scheme(): prepends http:// to bare Ollama hosts like 192.168.1.50:11434
• Add _build_headers(): omits Authorization header when api_key is empty
• Add _parse_openai_response(): returns success=False with clear message when choices is empty
• Honour OLLAMA_HOST, OLLAMA_MODEL, OPENAI_BASE_URL, OPENAI_MODEL, EOS_LLM_* env vars
• Add tests/unit/test_llm_client.py — 35 tests across 9 test classes, zero network calls
• Add PackageRecipe.to_dict() using external YAML key names (package, build) for round-trip correctness
• Fix F811 duplicate import shutil in test_build_dir_resolution.py
• Fix E402 mid-file imports in test_ci_gate.py
• Fix W292 missing newline in test_package_recipe.py
• Fix wrong # type: ignore[attr-defined] → [arg-type] in plugins/__init__.py

Testing

• Unit tests pass (ctest --test-dir build --output-on-failure)
• Integration tests pass
• Manual testing performed
• New tests added for new functionality

ruff check .      →  All checks passed! ✅
pytest tests/ -q  →  715 passed, 1 skipped, 0 failed ✅
                     (master was: 669 passed, 10 failed)

Pre-Submission Checklist

• Code compiles without warnings (-Wall -Wextra -Werror for C)
• All existing tests pass
• New tests added for new functionality
• Documentation updated if API changed
• Commit messages follow <type>(<scope>): <description> convention
• Branch is rebased on latest master

Related Issues

Addresses the same LLM URL issues noted in PR #120 (never merged).
Addresses the same lint gate issue noted in PR #122 (never merged).
Addresses the same to_dict() gap as PRs #119 and #124 (never merged).
Consolidated as a single coherent fix to keep review surface small.

Screenshots / Logs

$ ruff check .
All checks passed!

$ pytest tests/ -q
715 passed, 1 skipped in 13.08s

Additional Notes

All 35 new test_llm_client tests run fully offline — no Ollama, no API keys needed in CI.