mars: provision the Mnemosyne memory provider for Hermes

Mnemosyne isn't bundled with the official image; third-party PyPI plugin.
Built as a side venv + plugin symlink inside hermesHome so it lands
inside HERMES_WRITE_SAFE_ROOT and survives image rebuilds. Pinned
requirements captured from a validated live install.

hosts/mars/mnemosyne/requirements.txt

@@ -0,0 +1,46 @@
+# Pinned requirements for a Mnemosyne side-venv on mars.
+#
+# Hermes vendors its own Python (the official image's venv) and deliberately
+# stays minimal: no pip module inside it, PEP 668 external-management on top.
+# Installing provider packages straight into that interpreter would fight the
+# image on every rebuild, so Mnemosyne (and its plugin wrapper) live in their
+# own venv instead — see the provisioning unit in hosts/mars/hermes-agent.nix.
+#
+# Freeze captured 2026-09-19 from a verified container-side install of
+# `mnemosyne-memory[embeddings]` + `mnemosyne-hermes` — side venv at
+# $HERMES_HOME/mnemosyne-venv, activated via $HERMES_HOME/plugins/mnemosyne.
+# Versions pinned exactly; transitive deps frozen for reproducibility
+# (onnxruntime/numpy drift under a long-lived SQLite state dir is what a
+# freeze is here to prevent).
+#
+anyio==4.15.0
+certifi==2026.7.22
+charset-normalizer==3.5.1
+click==8.5.0
+fastembed==0.8.0
+filelock==3.32.5
+flatbuffers==25.12.19
+fsspec==2026.7.0
+h11==0.16.0
+hf-xet==1.6.0
+httpcore==1.0.9
+httpx==0.28.1
+huggingface-hub==1.32.0
+idna==3.19
+loguru==0.7.3
+mmh3==5.3.0
+mnemosyne-hermes==0.5.0
+mnemosyne-memory==3.15.1
+numpy==2.5.3
+onnxruntime==1.30.0
+packaging==26.3
+pillow==12.3.0
+protobuf==7.36.1
+py-rust-stemmers==0.1.8
+pyyaml==6.0.3
+requests==2.34.2
+sqlite-vec==0.1.9
+tokenizers==0.23.2
+tqdm==4.70.0
+typing-extensions==4.16.0
+urllib3==2.7.0