feat: update hbc via hb_install.sh instead of code patching

Server now sends a bare UPD command; client runs hb_install.sh to
reinstall from the package registry, then restarts. hb_install.sh
also copies itself alongside hbc on client installs.

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

hbd/client/main.py

@@ -14,7 +14,6 @@ import signal
 import socket
 import sys
 import time
-from hashlib import md5
 from logging.handlers import SysLogHandler
 from pathlib import Path
 from typing import Dict, List, Optional
@@ -204,55 +203,52 @@ async def handle_command(conn: AsyncConnection, msg: dict):
     await conn.sendto(response)
 
 
-async def handle_update(conn: AsyncConnection, msg: dict):
-    """Handle self-update from server."""
-    import codecs
+async def handle_update(conn: AsyncConnection, _msg: dict):  # pyright: ignore[reportUnusedParameter]
+    """Handle self-update by running hb_install.sh."""
     import shutil
-    
+
     logger = logging.getLogger("hbc.update")
-    
+
+    installer = shutil.which("hb_install.sh")
+    if installer is None:
+        candidate = Path(sys.argv[0]).parent / "hb_install.sh"
+        if candidate.exists():
+            installer = str(candidate)
+
+    if installer is None:
+        error = "hb_install.sh not found in PATH or alongside hbc"
+        logger.error(error)
+        await conn.sendto({"service": "update", "msg": error})
+        return
+
+    logger.info(f"Running installer: {installer}")
     try:
-        code = codecs.decode(msg["code"], "base64").decode()
-        csum = msg["csum"]
+        proc = await asyncio.create_subprocess_exec(
+            installer, "client",
+            stdout=asyncio.subprocess.PIPE,
+            stderr=asyncio.subprocess.STDOUT,
+        )
+        out, _ = await asyncio.wait_for(proc.communicate(), timeout=120)
+    except asyncio.TimeoutError:
+        error = "Installer timed out"
+        logger.error(error)
+        await conn.sendto({"service": "update", "msg": error})
+        return
     except Exception as e:
-        error = f"Missing code/csum: {e}"
+        error = f"Installer failed: {e}"
         logger.error(error)
         await conn.sendto({"service": "update", "msg": error})
         return
-    
-    # Verify checksum
-    m = md5()
-    m.update(code.encode())
-    if m.hexdigest() != csum:
-        error = "Checksum mismatch"
+
+    if proc.returncode != 0:
+        error = f"Installer exited {proc.returncode}: {out.decode().strip()}"
         logger.error(error)
         await conn.sendto({"service": "update", "msg": error})
         return
-    
-    # Backup current file
-    fn = sys.argv[0]
-    ofn = f"{fn}.sav"
-    try:
-        shutil.copy2(fn, ofn)
-    except Exception as e:
-        error = f"Backup failed: {e}"
-        logger.error(error)
-        await conn.sendto({"service": "update", "msg": error})
-        return
-    
-    # Write new code
-    try:
-        with open(fn, "w") as fh:
-            fh.write(code)
-    except Exception as e:
-        error = f"Write failed: {e}"
-        logger.error(error)
-        await conn.sendto({"service": "update", "msg": error})
-        return
-    
+
     logger.info("Update successful, restart required")
     await conn.sendto({"service": "update", "msg": "OK"})
-    
+
     # Trigger restart
     global dorestart
     dorestart = True