Install Hermes once; contained sessions run the pre-built environment

[renmengye]

Contained Hermes sessions ran uv run --project <clone>, so every session reinstalled Hermes's dependency tree into its per-run home before the model saw a token (measured: about 2–4 minutes per session on a cluster filesystem). They also could not start at all: uv run --project installs hermes-agent itself as an editable package, which writes build metadata into the clone, and the clone is bound read-only.

Claude Code and Codex are pinned binaries installed once and bound read-only; this makes Hermes the same.

Changes

• scripts/install_hermes.sh: after pinning and verifying the source, builds the runtime once per pinned commit at <repo>.runtime/<sha>/: a uv-managed standalone Python (so the interpreter resolves at the same path inside the container) and a venv (uv sync --frozen --no-install-project). A completion marker makes reruns a no-op; a lock refuses concurrent installs; the download cache is removed afterwards.
• HermesHarness: runs <runtime>/venv/bin/python -B <repo>/run_agent.py directly. No uv at session time. Contained sessions bind the source and the runtime read-only. A missing or incomplete runtime is an error result naming the installer; there is no per-session fallback.
• outerloop init: installs Hermes when a judge lens uses it (respecting --no-install-harness) and records REVIEW_HERMES_REPO.
• Docs and CHANGELOG updated.

Upgrading: existing Hermes deployments rerun bash scripts/install_hermes.sh once to build the runtime; until then Hermes lenses return the installer error instead of starting.

Verified

• Full gate: 2158 passed, 2 skipped; ruff, format, mypy clean.
• On a Slurm cluster: install built the runtime in about 4 minutes (rerun: 5 s); a contained verify session through this branch ran with no install step and filed its verdict. The same case with per-session installs took about 160 s longer.

🤖 Generated with Claude Code

[github-actions]

Round 1 — reviewed head a553ba2c — reviewer summarizer:hermes/gpt-5.6-terra over coverage+credentials+deployment+general+lifecycle+prose.

terra
Advisory findings from outerloop — the code owner decides. Reply to disagree; the outerloop:no-review label opts this PR out.

Verdict: nothing blocking — 1 advisory note.

1 finding attached to the lines below.

Merged 1 finding. Rejected findings: none; the remaining lenses reported no findings.

[github-actions]

Round 1 — reviewed head 0379c005 — reviewer hermes/gpt-5.6-terra.

terra
Advisory findings from outerloop — the code owner decides. Reply to disagree; the outerloop:no-review label opts this PR out.

Verdict: no defects found.

[renmengye]

Compatibility statement (added for the 0.3.0rc1 release audit, per RELEASING.md).

• Surfaces: the persisted Hermes runtime layout and its completion marker; the launch-time runtime reader.
• Oldest state read: a source-only (v0.2.1) Hermes checkout is not used until the runtime is installed; a missing runtime fails clearly at preflight rather than mid-session.
• First tick after upgrade: run outerloop harness upgrade hermes before Hermes sessions launch; other backends are unaffected.
• Rollback: older kernels ignore the runtime directory and use the source checkout.
• Fixtures: source-only installation, failure, retry and reuse (F16).