fix(plugin): bind adapter to real Hermes gateway API; add contract-test gate

- Resolve the Hermes gateway API lazily via get_adapter_class() so the adapter
  always inherits the real gateway.platforms.base.BasePlatformAdapter instead
  of the ImportError fallback stub (root cause of the AttributeError:
  'set_message_handler' crash at gateway startup).
- Pass Platform('meshtastic') enum to super().__init__ and align
  connect(*, is_reconnect=False) -> bool with the gateway contract.
- Split pure formatting utils into formatting.py; remove the stub fallback.
- Add tests/contract (L0-L3): real-base binding, ABC instantiation, gateway
  run.py wiring replay, signature and event-shape conformance, run against
  hermes-agent pinned to the deployed image source (v2026.8.31).
- Add scripts/contract-test.sh and a contract-test CI job; release publish
  now requires contract tests to pass.
- Untrack stray __pycache__ artifacts.

scripts/contract-test.sh

@@ -0,0 +1,61 @@
+#!/usr/bin/env bash
+# Gateway contract tests for hermes-meshtastic.
+#
+# Runs the plugin's contract suite (tests/contract/) against the REAL Hermes
+# gateway API, pinned to the same upstream commit the deployed container image
+# is built from (NousResearch/hermes-agent @ v2026.8.31 — the image tag used in
+# k8s-flux apps/base/coder/hermes-agent).
+#
+# Why: the adapter used to be developed by guessing the gateway API and only
+# failing at gateway startup after a release (AttributeError: ... no attribute
+# 'set_message_handler'). These tests replay the gateway's adapter bootstrap
+# (registry registration -> factory -> set_* wiring) so API drift fails here,
+# in seconds, without deploying.
+#
+# Requires: uv (https://docs.astral.sh/uv/) and network on first run.
+#
+# Usage:  scripts/contract-test.sh
+set -euo pipefail
+
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+PLUGIN_DIR="$REPO_ROOT/plugin"
+VENV="$PLUGIN_DIR/.venv-contract"
+HERMES_SRC="$PLUGIN_DIR/.hermes-src"
+HERMES_TAG="${HERMES_TAG:-v2026.8.31}"   # must match k8s-flux hermes image tag
+HERMES_COMMIT="${HERMES_COMMIT:-29112bef099274229cadff79cdff7bf7b99c4b77}"
+
+if ! command -v uv >/dev/null 2>&1; then
+  echo "error: uv is required (https://docs.astral.sh/uv/)" >&2
+  exit 1
+fi
+
+if [ ! -d "$HERMES_SRC/.git" ]; then
+  echo "== cloning hermes-agent @ $HERMES_TAG (deployed image source) =="
+  git clone --depth 1 --branch "$HERMES_TAG" \
+    https://github.com/NousResearch/hermes-agent.git "$HERMES_SRC"
+fi
+actual="$(git -C "$HERMES_SRC" rev-parse HEAD)"
+if [ "$actual" != "$HERMES_COMMIT" ]; then
+  echo "error: $HERMES_SRC is at $actual, expected $HERMES_COMMIT ($HERMES_TAG)." >&2
+  echo "       Refresh deliberately: HERMES_TAG=<new tag> scripts/contract-test.sh" >&2
+  exit 1
+fi
+
+if [ ! -x "$VENV/bin/python" ]; then
+  echo "== creating contract venv (python 3.13, matching the Hermes image) =="
+  uv venv --python 3.13 "$VENV"
+fi
+uv pip install --python "$VENV/bin/python" -q -e "$HERMES_SRC"
+uv pip install --python "$VENV/bin/python" -q pytest
+
+echo "== running contract tests (HERMES_CONTRACT_REQUIRED=1) =="
+(
+  cd "$PLUGIN_DIR"
+  HERMES_CONTRACT_REQUIRED=1 "$VENV/bin/python" -m pytest tests/contract -q "$@"
+)
+
+echo "== running standalone unit tests (no gateway needed) =="
+(
+  cd "$PLUGIN_DIR"
+  "$VENV/bin/python" -m pytest tests/test_adapter.py -q
+)