Community edition merge lane and compliance auditor

Found while reducing the CE runner doctrine (Task 10841). Two CE personas are honestly told to fail, because the CE tree lacks what they need: 1. **Merge lane**: PR code must only run through a sandboxed gate (cloud: `tools/merge_lane.py gate`, under bwrap). The CE tree ships no such gate, so a CE merge-lane runner merges nothing and `task_fail`s, while implementers on a lane-active CE project settle on `queued` and their PRs wait forever. Either ship the sandboxed gate in the CE tree/node bundle, or refuse to turn the lane on for a CE project. 2. **Compliance auditor**: its prompt needs `jaah-audit`, which the CE node bundle never installs (`infra/community-edition/node/stage_bundle.py` closure omits `packages/governance`; no launcher). Stage it, or hide the persona in CE. Out of scope: the CE doctrine prose itself (Task 10841), cloud behaviour. Done means: - A lane-active CE project merges a queued PR end to end (or the CE console refuses to enable the lane, with a clear message). - A CE compliance-auditor run finds `jaah-audit` on the node (or the persona is not offered in CE).