M1.5 accepted: the tests run over a published image

- The Dockerfile's test stage stacks on TEST_BASE: this build's agent by
  default, or a published image. It adds only the test tools (uv export
  of the dev group into the image's environment), never reinstalling the
  agent, so the suite tests the image as published.
- scripts/e2e.sh --image passes NISSE_E2E_MODEL into the container.
- The plan marks M1.5 done: v0.1.0's published image passed the whole e2e
  suite (9 of 9, 11m37s), with the release's own tests over it.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPQ14L3LikyefCMFBqEbKE

scripts/e2e.sh

@@ -23,6 +23,8 @@ if [ "${1:-}" = "--image" ]; then
     mkdir -p "$runs"
     secrets=()
     [ -f .env ] && secrets=(--env-file .env)
+    # The model, if overridden here, reaches the tests inside too.
+    [ -n "${NISSE_E2E_MODEL:-}" ] && secrets+=(-e "NISSE_E2E_MODEL=$NISSE_E2E_MODEL")
     # Host networking: the suite reaches Matrix, Gitea and LiteLLM as here.
     exec docker run --rm --network host "${secrets[@]}" \
         -e NISSE_E2E_RUNS=/runs -v "$runs:/runs" \