ops: systemd units for auditor + context7 bridge

Promotes two previously manual-start Bun services to systemd
so they survive restarts + run continuously.

- ops/systemd/lakehouse-auditor.service — polls Gitea every 90s,
  runs 4 audit checks per PR head SHA, posts commit status + review
  comment. Runs as root to match existing lakehouse-* service
  conventions on this host; can read /home/profit/.git-credentials
  (0600 profit:profit).
- ops/systemd/lakehouse-context7-bridge.service — HTTP wrapper on
  :3900 for Phase 45 doc-drift detection. Decoupled from gateway;
  runs independently.
- ops/systemd/install.sh — idempotent installer (copy → daemon-reload
  → enable --now). Prints post-install active/enabled status.
- ops/systemd/README.md — run/stop/logs/pause docs.

Pause control stays per-service (bot.paused / auditor.paused files
at repo root). Not wired to branch protection yet — the auditor's
commit status is currently advisory, not enforcing. Flip via Gitea
branch_protections API when confident.

ops/systemd/README.md

@@ -0,0 +1,57 @@
+# Lakehouse systemd units
+
+Service definitions for long-running Lakehouse sidecars that aren't the
+Rust gateway itself. The gateway has its own pre-existing unit
+(`lakehouse.service`) that was configured at initial deploy time and
+isn't tracked here.
+
+## Units
+
+| File | Service | Port | Purpose |
+|---|---|---|---|
+| `lakehouse-auditor.service` | `lakehouse-auditor` | n/a | Polls Gitea for open PRs, runs four checks (static / dynamic / inference / KB query), posts commit-status + review comment. Hard-blocks merges when claims aren't backed. |
+| `lakehouse-context7-bridge.service` | `lakehouse-context7-bridge` | `:3900` | HTTP wrapper around context7's public API for Phase 45 doc-drift detection. |
+
+## Install
+
+```bash
+sudo bash ops/systemd/install.sh
+```
+
+Idempotent. Copies units to `/etc/systemd/system/`, reloads, enables + (re)starts both services.
+
+## Operate
+
+```bash
+# Status
+systemctl status lakehouse-auditor
+systemctl status lakehouse-context7-bridge
+
+# Live logs
+journalctl -u lakehouse-auditor -f
+
+# Restart
+systemctl restart lakehouse-auditor
+
+# Stop (won't restart until enable + start again)
+systemctl stop lakehouse-auditor
+```
+
+## Pause the auditor without stopping
+
+```bash
+touch /home/profit/lakehouse/auditor.paused   # skip cycles until removed
+rm    /home/profit/lakehouse/auditor.paused   # resume
+```
+
+## Env toggles on the auditor (edit the unit file, `systemctl daemon-reload`, restart)
+
+```
+LH_AUDITOR_RUN_DYNAMIC=1    # include the hybrid fixture on every audit
+                            # default off — fixture mutates live playbook state
+LH_AUDITOR_SKIP_INFERENCE=1 # skip cloud inference for fast/cheap runs
+```
+
+## Why both services run as root
+
+To match the existing `lakehouse.service` + `mcp-server` + `observer` conventions on this host. Hardening to a dedicated unprivileged user is a follow-up: would need PATH adjustment for `bun`, credential file accessibility (the auditor reads `/home/profit/.git-credentials` which is `0600 profit:profit` — root reads fine, a non-profit non-root user wouldn't).