v0.126.0: a fetch failure is not a wrong recovery code (R-224)

A hub the agent could not reach was reported to the customer as a bad recovery
code. Measured live 2026-08-05 (CAMPAIGN-11 F3): hub firewalled off, a CORRECT
current code, and the customer told it did not open their package — in 0.0556s
against ~1.0s for a real unseal. No unseal was attempted.

The discriminator existed here and this boundary threw it away: recover.go
fails at four distinguishable points and the local-api handler had cases for
two, with a default answering 'the recovery code did not open the sealed
bundle, OR the bundle could not be fetched'.

escrow.ErrBundleFetch now joins the fetch leg and the handler routes it to 502
with its own words — the code was NOT used. 502 not 4xx: the request was not
bad, an upstream dependency failed. Four situations, four statuses: 502 fetch /
400 fetched-and-refused / 404 no bundle / 409 predates the field. The
controller classifies on the STATUS and never parses the sentence.

A GREEN TEST NAMED THIS DEFECT AND DID NOT PREVENT IT.
TestRecoverOffsiteRepoPassword_FetchErrorIsDistinct has said since v0.125.0
that the operator must not be sent to re-read their code because the hub was
unreachable — and passed throughout, because it asserted this package's error
STRING one layer below the merge, and a string is not something a caller can
branch on. Re-pointed at the sentinel, with a consequence-level twin asserting
the status.

Red-proofs: removing the %w join fails the sentinel test; deleting the handler
case makes fetch and wrong-code both answer 400 with the wrong-code sentence.

29 packages ok, vet clean, agent gates OK.

internal/escrow/recover.go

@@ -19,10 +19,27 @@ import (
 // keeps that property: it takes R as an argument, passes it straight through, and holds no copy.
 // Callers must clear their own reference (the `R = ""` discipline in cmd/felhom-agent).
 //
-// The errors below are DISTINCT on purpose. "no blob", "wrong code" and "the blob predates the field"
-// are three different situations for the operator and only one of them is a fault.
+// The errors below are DISTINCT on purpose. "could not fetch", "no blob", "wrong code" and "the blob
+// predates the field" are FOUR different situations for the operator and only one of them is a fault.
+//
+// ⚠ THERE WERE THREE, AND THE FOURTH WAS THE DEFECT (R-224, 2026-08-06). This comment said "three"
+// and named "no blob", "wrong code" and "predates the field" — while a FAILED FETCH was wrapped as an
+// anonymous error and fell through the caller's `default` branch into the wrong-code message. So a
+// hub that could not be reached was reported to the customer as a bad recovery code.
+//
+// Measured live on 2026-08-05 (CAMPAIGN-11 F3): with the hub REJECTed at the appliance's firewall and
+// a CORRECT current recovery code, the customer was told the code did not open their package — in
+// 0.0556 s, when a real unseal costs ~1 s of scrypt. The agent's own log carried the truth the whole
+// time (`escrow: fetching the sealed bundle: hub: transport error: … no route to host`) and the HTTP
+// boundary threw it away.
+//
+// The discriminator therefore has to be a VALUE, not a log line — that is what ErrBundleFetch is.
 
 var (
+	// ErrBundleFetch — the sealed bundle could not be FETCHED (the hub refused, was unreachable, or
+	// the transport failed). **The recovery code was never used**, so nothing about it is known and
+	// nothing may be said about it. Wraps the underlying cause for the operator log; carries no secret.
+	ErrBundleFetch = errors.New("escrow: the sealed bundle could not be fetched")
 	// ErrNoEscrowBlob — the hub holds no sealed bundle for this host. Not a fault: no ceremony has run.
 	ErrNoEscrowBlob = errors.New("escrow: the hub holds no sealed identity bundle for this host (no ceremony has run)")
 	// ErrNoResticPassword — the bundle opened, but carries no repository password. Real and expected
@@ -58,7 +75,11 @@ func (r OffsiteKeyRecoverer) RecoverOffsiteRepoPassword(ctx context.Context, rec
 	}
 	blob, present, err := r.Fetch(ctx)
 	if err != nil {
-		return "", fmt.Errorf("escrow: fetching the sealed bundle: %w", err) // carries no secret
+		// R-224: joined with ErrBundleFetch so the caller can classify by VALUE. The cause stays
+		// wrapped for the operator log; neither carries a secret. Before this, the fetch failure was
+		// an anonymous error and the local-api handler's `default` branch reported it to the customer
+		// as a wrong recovery code.
+		return "", fmt.Errorf("%w: %w", ErrBundleFetch, err)
 	}
 	if !present || len(blob) == 0 {
 		return "", ErrNoEscrowBlob