fix: enrollment FK race + log-when-rejected; runbook fixes from dry-run

The smoke runbook caught a real bug: ConsumeEnrollmentToken was
inserting into host_credentials (FK -> hosts) inside the same tx as
the token burn, but the host row didn't exist yet — CreateHost
runs in the *next* statement. The agent saw a generic 401 with no
clue why.

Fix: drop the host_credentials insert from ConsumeEnrollmentToken;
the HTTP handler now does Consume -> CreateHost ->
SetHostCredentials. SetHostCredentials failure is logged loudly
but doesn't fail the enrol — operator recovers via PUT
/api/hosts/{id}/repo-credentials.

Adds slog.Warn lines on both 401 paths in handleAgentEnroll so the
underlying cause is visible in server logs (the wire response stays
generic to avoid leaking which step failed).

Test: TestEnrollmentTransfersRepoCreds rewritten to mirror the new
order (consume -> create host -> SetHostCredentials).

Runbook (docs/e2e-smoke.md): rest-server moved off 8000 (commonly
in use); URLs use trailing slash on the rest path; clarified that
secrets_key is minted on first agent start, not at enrol time.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/server/http/enrollment.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"fmt"
+	"log/slog"
 	stdhttp "net/http"
 	"strings"
 	"time"
@@ -98,12 +99,14 @@ func (s *Server) handleAgentEnroll(w stdhttp.ResponseWriter, r *stdhttp.Request)
 	// the token, which is about to disappear).
 	encForHost, err := s.rebindTokenCreds(r.Context(), tokHash, hostID)
 	if err != nil {
+		slog.Warn("enrollment: rebind token creds failed", "err", err)
 		writeJSONError(w, stdhttp.StatusUnauthorized, "invalid_token",
 			"token unknown, expired, or already used")
 		return
 	}
 
-	if err := s.deps.Store.ConsumeEnrollmentToken(r.Context(), tokHash, hostID, encForHost); err != nil {
+	if err := s.deps.Store.ConsumeEnrollmentToken(r.Context(), tokHash, hostID); err != nil {
+		slog.Warn("enrollment: consume token failed", "err", err)
 		writeJSONError(w, stdhttp.StatusUnauthorized, "invalid_token",
 			"token unknown, expired, or already used")
 		return
@@ -131,6 +134,18 @@ func (s *Server) handleAgentEnroll(w stdhttp.ResponseWriter, r *stdhttp.Request)
 		return
 	}
 
+	// Promote the encrypted repo creds onto the freshly-created host
+	// row. If this fails for any reason we log loudly but still
+	// return the bearer — the operator recovers via PUT
+	// /api/hosts/{id}/repo-credentials. Failing the whole enrolment
+	// here would leave a half-burned token + an orphan host.
+	if encForHost != "" {
+		if err := s.deps.Store.SetHostCredentials(r.Context(), hostID, encForHost); err != nil {
+			slog.Error("enrollment: set host credentials failed",
+				"host_id", hostID, "err", err)
+		}
+	}
+
 	_ = s.deps.Store.AppendAudit(r.Context(), store.AuditEntry{
 		ID:         ulid.Make().String(),
 		Actor:      "system",