fix(supervisor): improve alert messages with category prefix and error snippet

Each alert now includes a neutral category tag ([extract], [transform],
[export], [deploy], [supervisor]) and the first line of the error, so
notifications are actionable without revealing tech stack details on the
public free ntfy tier.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/padelnomics/supervisor.py

@@ -192,9 +192,9 @@ def run_workflow(conn, workflow: dict) -> None:
         entry_fn = getattr(module, entry_name)
         entry_fn()
         logger.info("Workflow %s completed successfully", workflow["name"])
-    except Exception:
+    except Exception as exc:
         logger.exception("Workflow %s failed", workflow["name"])
-        send_alert(f"Workflow '{workflow['name']}' failed")
+        send_alert(f"[extract] {type(exc).__name__}: {str(exc)[:100]}")
         raise
 
 
@@ -233,8 +233,8 @@ def run_due_workflows(conn, workflows: list[dict]) -> bool:
 # Transform + Export + Deploy
 # ---------------------------------------------------------------------------
 
-def run_shell(cmd: str, timeout_seconds: int = SUBPROCESS_TIMEOUT_SECONDS) -> bool:
-    """Run a shell command. Returns True on success."""
+def run_shell(cmd: str, timeout_seconds: int = SUBPROCESS_TIMEOUT_SECONDS) -> tuple[bool, str]:
+    """Run a shell command. Returns (success, error_snippet)."""
     logger.info("Shell: %s", cmd)
     result = subprocess.run(
         cmd, shell=True, capture_output=True, text=True, timeout=timeout_seconds
@@ -242,29 +242,31 @@ def run_shell(cmd: str, timeout_seconds: int = SUBPROCESS_TIMEOUT_SECONDS) -> bo
     if result.returncode != 0:
         logger.error("Shell failed (rc=%d): %s\nstdout: %s\nstderr: %s",
                       result.returncode, cmd, result.stdout[-500:], result.stderr[-500:])
-        return False
-    return True
+        raw = (result.stderr or result.stdout).strip()
+        snippet = next((ln.strip() for ln in raw.splitlines() if ln.strip()), raw)[:120]
+        return False, snippet
+    return True, ""
 
 
 def run_transform() -> None:
     """Run SQLMesh — it evaluates model staleness internally."""
     logger.info("Running SQLMesh transform")
-    ok = run_shell(
+    ok, err = run_shell(
         "uv run sqlmesh -p transform/sqlmesh_padelnomics plan prod --auto-apply",
     )
     if not ok:
-        send_alert("SQLMesh transform failed")
+        send_alert(f"[transform] {err}")
 
 
 def run_export() -> None:
     """Export serving tables to analytics.duckdb."""
     logger.info("Exporting serving tables")
-    ok = run_shell(
+    ok, err = run_shell(
         f"DUCKDB_PATH={DUCKDB_PATH} SERVING_DUCKDB_PATH={SERVING_DUCKDB_PATH} "
         f"uv run python src/padelnomics/export_serving.py"
     )
     if not ok:
-        send_alert("Serving export failed")
+        send_alert(f"[export] {err}")
 
 
 def web_code_changed() -> bool:
@@ -365,11 +367,11 @@ def tick() -> None:
         # Deploy web app if code changed
         if os.getenv("SUPERVISOR_GIT_PULL") and web_code_changed():
             logger.info("Web code changed — deploying")
-            ok = run_shell("./deploy.sh")
+            ok, err = run_shell("./deploy.sh")
             if ok:
-                send_alert("Deploy succeeded")
+                send_alert("[deploy] ok")
             else:
-                send_alert("Deploy FAILED — check journalctl -u padelnomics-supervisor")
+                send_alert(f"[deploy] failed: {err}")
     finally:
         conn.close()
 
@@ -386,9 +388,9 @@ def supervisor_loop() -> None:
         except KeyboardInterrupt:
             logger.info("Supervisor stopped (KeyboardInterrupt)")
             break
-        except Exception:
+        except Exception as exc:
             logger.exception("Supervisor tick failed — backing off %ds", BACKOFF_SECONDS)
-            send_alert("Supervisor tick failed")
+            send_alert(f"[supervisor] {type(exc).__name__}: {str(exc)[:100]}")
             time.sleep(BACKOFF_SECONDS)
         else:
             time.sleep(TICK_INTERVAL_SECONDS)