fix: 15 bug fixes across orchestrator, runner, backtest, and infrastructure

Critical:
- strategy_orchestrator: fix IndentationError that prevented import (line 764)
- factor_runner: fix literal 'sys.executable' string → variable (line 966)

High (path bugs causing wrong directories):
- backtest_engine: fix results_path depth (3→4 .parent hops)
- results_db: fix factors_dir/failed_dir depth (3→4 .parent hops)
- factor_runner: eliminate run_id variable shadowing (parallel_run_id/db_run_id)
- model_runner: fix DB connection leak on add_backtest exception
- optuna_optimizer: fix imported logger shadowed by module-level reassignment

Medium:
- env: handle non-UTF-8 Docker build output with errors='replace'
- env: guard conda env list parsing against empty lines
- factor_runner: add check=False + stderr logging for full-data subprocess
- strategy_orchestrator: log exec() exceptions at ERROR level with traceback
- strategy_orchestrator: warn on unreplaced {{template}} variables in prompts

Low:
- factor_runner: guard IC_max.index access against scalar (AttributeError)
- predix_parallel: close log file handle on Popen failure
- predix_rebacktest_strategies: replace 4 bare except: with except Exception:

scripts/predix_parallel.py

@@ -230,16 +230,20 @@ class ParallelRunner:
         log_path = self.project_root / run_state.log_file
         log_f = open(log_path, "a", encoding="utf-8")
 
-        # Start subprocess
-        run_state.process = subprocess.Popen(
-            cmd,
-            env=env,
-            cwd=str(self.project_root),
-            stdout=log_f,
-            stderr=subprocess.STDOUT,
-        )
-        run_state.status = "running"
-        run_state.start_time = datetime.now()
+        try:
+            # Start subprocess
+            run_state.process = subprocess.Popen(
+                cmd,
+                env=env,
+                cwd=str(self.project_root),
+                stdout=log_f,
+                stderr=subprocess.STDOUT,
+            )
+            run_state.status = "running"
+            run_state.start_time = datetime.now()
+        except Exception:
+            log_f.close()
+            raise
 
         console.print(
             f"[dim]  ▶️  Run {run_state.run_id} started (PID: {run_state.process.pid}, "