v0.108.0: hub-verified escrow auto-confirm on current-password hash match (SLICE 3)

EscrowAutoConfirmer flips pending->escrowed ONLY when sha256(local repo
password) matches the ACK's restic_pw_sha256 (blob-presence alone never
confirms — red-proofed). Mismatch warns once per hash naming the ceremony;
never un-confirms; wipes the staged secret on flip. Pinned cross-repo hash
vector; manual confirm deprecated to a legacy-blob fallback.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PSK5g6qYLknKj8u3QAFEr6

controller/internal/backup/offbox.go

@@ -3,6 +3,7 @@ package backup
 import (
 	"context"
 	"crypto/rand"
+	"crypto/sha256"
 	"encoding/hex"
 	"encoding/json"
 	"fmt"
@@ -188,6 +189,26 @@ func (m *Manager) ApplyOffsiteTarget(ctx context.Context, tgt *settings.OffboxTa
 	return nil
 }
 
+// HashResticPassword is the CANONICAL hasher for the offsite repo password (SLICE 3 hub-verified escrow
+// auto-confirm): sha256 hex of the TRIMMED password string — the SAME convention as the agent's
+// escrow.HashResticPassword (both sides TrimSpace their file reads; pinned by the SAME cross-repo test
+// vector in felhom-agent). The hash of a 256-bit random secret is non-reversible and non-brute-forceable —
+// safe to log/compare; the PASSWORD itself is never logged.
+func HashResticPassword(pw string) string {
+	sum := sha256.Sum256([]byte(strings.TrimSpace(pw)))
+	return hex.EncodeToString(sum[:])
+}
+
+// OffboxRepoPasswordHash returns the canonical hash of the local repo password (false when no password
+// file exists — nothing to match; the auto-confirm check skips).
+func (m *Manager) OffboxRepoPasswordHash() (string, bool) {
+	pw, err := os.ReadFile(m.offboxPwPath())
+	if err != nil {
+		return "", false
+	}
+	return HashResticPassword(string(pw)), true
+}
+
 // PushOffboxPasswordForEscrow reads the 0600 repo password and hands it to `stage` (the agent push), so
 // the web/handler caller never sees the value — used by the enable flow to escrow-stage the offsite key.
 func (m *Manager) PushOffboxPasswordForEscrow(ctx context.Context, stage func(ctx context.Context, pw string) error) error {