fix(smoke): wire mechanistic smoke into mise and guard TMP_DIR

- Initialize TMP_DIR before trap to prevent unbound variable on early exit
- Add e2e:mechanistic-smoke mise task with gateway setup
- Document mechanistic smoke in policy-advisor README

Author: mesutoezdil

e2e/policy-advisor/README.md

@@ -52,3 +52,18 @@ bash e2e/policy-advisor/test.sh
 Requires Docker, `agent_policy_proposals_enabled=true`, and a GitHub token with
 contents write on the repository. The test auto-resolves the token from
 `DEMO_GITHUB_TOKEN`, `GITHUB_TOKEN`, `GH_TOKEN`, or `gh auth token`.
+
+## Mechanistic smoke
+
+Lightweight regression for the L4 CONNECT deny → mechanistic chunk pipeline.
+No GitHub token or LLM required.
+
+```bash
+mise run e2e:mechanistic-smoke
+```
+
+Or manually against a running gateway with `agent_policy_proposals_enabled=true`:
+
+```bash
+OPENSHELL_BIN=target/debug/openshell bash e2e/policy-advisor/mechanistic-smoke.sh
+```

e2e/policy-advisor/mechanistic-smoke.sh

@@ -43,6 +43,8 @@ step() { printf "\n${BOLD}${CYAN}==> %s${RESET}\n\n" "$1"; }
 ok()   { printf "  ${GREEN}✓${RESET} %s\n" "$*"; }
 fail() { printf "\n${RED}FAIL:${RESET} %s\n" "$*" >&2; exit 1; }
 
+TMP_DIR=""
+
 cleanup() {
     if [[ "$KEEP_SANDBOX" != "1" ]]; then
         "$OPENSHELL_BIN" sandbox delete "$SANDBOX" >/dev/null 2>&1 || true

tasks/test.toml

@@ -78,6 +78,13 @@ run = "e2e/rust/e2e-vm.sh"
 description = "Run smoke e2e against a standalone gateway with the Docker compute driver"
 run = "e2e/rust/e2e-docker.sh"
 
+["e2e:mechanistic-smoke"]
+description = "Run mechanistic L4 smoke against a Docker-backed gateway"
+run = [
+  "cargo build -p openshell-cli --features openshell-core/dev-settings",
+  "e2e/with-docker-gateway.sh bash -lc 'target/debug/openshell settings set --global --key agent_policy_proposals_enabled --value true --yes && OPENSHELL_BIN=$PWD/target/debug/openshell bash e2e/policy-advisor/mechanistic-smoke.sh'",
+]
+
 ["e2e:docker:gpu"]
 description = "Run GPU e2e against a standalone gateway with the Docker compute driver"
 env = { OPENSHELL_E2E_DOCKER_GPU = "1", OPENSHELL_E2E_DOCKER_TEST = "gpu_device_selection", OPENSHELL_E2E_DOCKER_FEATURES = "e2e-docker-gpu" }