Fix native workflow behavior and isolate path localization tests

[zhanghanduo]

Summary

Carries forward #36 and fixes its failing test_localize_absolute_path_inside_cwd. The test inherited FRONTIER_AGENT_WORKSPACE_DIR, so a split runtime workspace caused it to expect localization where the implementation correctly preserves absolute paths.

Explicitly isolate the workspace and inputs environment, and cover unset, same-directory, and symlinked workspace cases. The existing split-workspace test also clears the inputs override so it exercises the intended branch.

Original #36 changes preserve native workflow completion, authoritative loop telemetry, absolute project read paths, and ordinary non-root native behavior. This draft is an alternative because the original fork disallows maintainer edits and rejected the repair push. Repair-only commit: 5a84d62.

Validation

• Reproduced the original failure with an injected runtime workspace.
• 104 feature/native tests pass with that same injected environment after repair.
• Repository Ruff check and git diff --check pass.
• Linux CI passed: 1742 tests passed, plus Pyright, import smoke, release gates, and deployment validation. All CodeQL checks also passed.
• CI run: https://github.com/ApodexAI/FrontierAgent/actions/runs/36087025926