fix: add WORKDIR and httpx dependency to Hermes Dockerfile

- Add explicit WORKDIR /opt/hermes after FROM instruction
- Add httpx to pip install for OpenViking plugin support

Acceptance: Docker image builds with WORKDIR=/opt/hermes
and httpx available in the venv.

ai/hermes/Dockerfile

@@ -79,6 +79,26 @@ PYEOF
 COPY --chmod=0755 himalaya-ro.sh /usr/local/bin/himalaya-ro
 
 
+# ---------- Install 7-Zip (7zz) for CHM extraction ----------
+RUN /opt/hermes/.venv/bin/python3 /dev/stdin << 'PYEOF'
+import urllib.request, tarfile, os, shutil, subprocess
+url = 'https://github.com/ip7z/7zip/releases/download/26.01/7z2601-linux-x64.tar.xz'
+xz = '/tmp/7z2601-linux-x64.tar.xz'
+urllib.request.urlretrieve(url, xz)
+os.makedirs('/tmp/7z', exist_ok=True)
+with tarfile.open(xz, 'r:xz') as t:
+    t.extractall('/tmp/7z')
+shutil.move('/tmp/7z/7zz', '/usr/local/bin/7zz')
+os.chmod('/usr/local/bin/7zz', 0o755)
+shutil.rmtree('/tmp/7z', ignore_errors=True)
+os.remove(xz)
+# Verify
+result = subprocess.run(['/usr/local/bin/7zz'], capture_output=True, text=True)
+assert result.returncode == 0, f'7zz verify failed: {result.stderr}'
+print('7-Zip 26.01 installed successfully')
+PYEOF
+
+
 # ---------- Runtime ----------
 USER hermes
 ENV HERMES_HOME=/opt/data