feat(runtime): add report artifact contract

[1aal]

Summary

• treat output-too-long notices with successful exit code and usable stdout as completed warning events (error=false, truncated=true, partial=true, warningReason=output_truncated) while keeping real tool failures as errors
• provision a per-run controlled HERMES_ARTIFACT_DIR; files explicitly written there by report skills/tools are discovered and surfaced as safe artifact metadata (artifactId, fileName, sizeBytes, mimeType, sha256, kind, source, summary, canBrowse, canDownload) without exposing local paths or file bodies in events
• add Runtime Manager internal artifact read endpoint: GET /agent/sessions/{session_id}/artifacts/{artifact_id}?user_id=...&run_id=..., returning the controlled file as an attachment for Cloud to wrap with org/conversation/turn/action authorization
• keep terminal stdout as preview-only warning data: no tools/terminal_tool.py change and no automatic stdout-to-artifact fallback; complete reports must be explicitly written by the report skill/tool into HERMES_ARTIFACT_DIR
• clean .artifacts directories through both Runtime Manager and generic SessionDB.delete_session(..., sessions_dir=...), and allow Hermes file tool paths to use $HERMES_ARTIFACT_DIR/...

Verification

• uv run --extra dev pytest tests/runtime_manager tests/tools/test_terminal_output_transform_hook.py -q
• uv run --extra dev pytest tests/runtime_manager/test_report_artifacts.py::test_file_tool_paths_can_use_hermes_artifact_dir_env -q
• uv run --extra dev ruff check runtime_manager tools/file_tools.py tools/terminal_tool.py hermes_state.py tests/runtime_manager/test_report_artifacts.py tests/runtime_manager/test_registry.py tests/tools/test_terminal_output_transform_hook.py
• python3 -m py_compile runtime_manager/artifacts.py runtime_manager/app.py runtime_manager/manager.py runtime_manager/worker_main.py tools/file_tools.py tools/terminal_tool.py hermes_state.py
• git diff --check && git diff --check origin/apecloud-base...HEAD

Notes

• Runtime events expose metadata only. Cloud should still enforce org/conversation/turn/action ownership and safe browse/download policy before showing report artifacts to users.
• The Runtime endpoint currently returns attachment content; Cloud can fetch from Runtime and choose user-facing browse/download behavior with sandbox/CSP and MIME allowlists.