Phase 4 (Performance) + Phase 6 (Infrastructure) completion

Phase 4 — Performance:
- F1: SSH DialPool with key-by-host pooling and 5min idle TTL
- F2: In-memory entity lookup cache (TTL 60s, HTTP resolveEntityID)
- F3: Trigram GIN indexes on entities.slug and entities.name (migration 031)
- F4: Partial index on executions(classification_id) for auto-act (migration 032)
- Added missing RunOutput and RunStreaming in actuator/ (E3 gap fill)

Phase 6 — Infrastructure:
- H1: Infisical image pinned to v0.99.1
- H2: execworker daemon — polls pending executions with per-execution
  advisory locks, recovers orphaned running executions, wired as
  docker-compose service
- H3: splitSQL hardened with block comment and string-literal support,
  6 new edge-case tests (11 total)
- H4: Scheduler acquires pg_try_advisory_lock(0x01c05e6) at startup

internal/actuator/client.go

@@ -1,10 +1,12 @@
 package actuator
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"net"
 	"os"
+	"strings"
 	"time"
 
 	"golang.org/x/crypto/ssh"
@@ -99,3 +101,41 @@ func RunCombinedOutput(ctx context.Context, client *ssh.Client, cmd string) ([]b
 		return res.out, nil
 	}
 }
+
+// RunOutput runs cmd on an established client and returns stdout only.
+// Stderr is folded into the returned error so callers that parse stdout
+// as JSON (e.g. the scheduler's check scripts) don't get interleaved
+// stderr in the output stream.
+func RunOutput(ctx context.Context, client *ssh.Client, cmd string) ([]byte, error) {
+	session, err := client.NewSession()
+	if err != nil {
+		return nil, fmt.Errorf("create session: %w", err)
+	}
+	defer session.Close()
+
+	var outBuf, errBuf bytes.Buffer
+	session.Stdout = &outBuf
+	session.Stderr = &errBuf
+
+	type result struct {
+		runErr error
+	}
+	ch := make(chan result, 1)
+	go func() {
+		ch <- result{runErr: session.Run(cmd)}
+	}()
+
+	select {
+	case <-ctx.Done():
+		session.Close()
+		return nil, ctx.Err()
+	case res := <-ch:
+		if res.runErr != nil {
+			if errBuf.Len() > 0 {
+				return outBuf.Bytes(), fmt.Errorf("command: %w\nstderr: %s", res.runErr, strings.TrimSpace(errBuf.String()))
+			}
+			return outBuf.Bytes(), fmt.Errorf("command: %w", res.runErr)
+		}
+		return outBuf.Bytes(), nil
+	}
+}