agent v0.38.0: DR recipe — emit secret-free storage/guest/PBS half in host-report

DR recipe slice (agent half), grounded in SPIKE-dr-recipe-2026-06-16. Additive
`dr_recipe` host-report section = the non-secret reconstruction scaffolding the
operator must rebuild before PBS bytes can land. Built by pure
BuildDRRecipeHostHalf from facts the report already collects (no new reads):
guests[] sizing, drives[] (user-data by durable_id/role/mount/intent),
pve_storage[] (storage.cfg), pbs coordinates.

BOUNDARY (Phase-1 lesson): every field is an identifier/intent/size/coordinate —
never a key/password/token/hash/ENC:. PBS key stays in escrow; restic password
stays in escrow; the recipe names only the coordinates the restore targets.

Tests: BuildDRRecipeHostHalf selection, NoPBS, NoSecrets (boundary mirror),
dr_recipe key-set in the cross-repo golden contract test. recipe_version=1,
ignore-unknown on read.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/hub/report.go

@@ -26,6 +26,11 @@ type HostReport struct {
 
 	Cloudflared Cloudflared  `json:"cloudflared"`
 	AuditTail   []AuditEntry `json:"audit_tail"` // populated by a later slice
+
+	// DR recipe — the agent (storage/guest/PBS) half of the secret-free reconstruction recipe
+	// (SPIKE-dr-recipe-2026-06-16). Derived from the facts above; carries ONLY identifiers/intents/
+	// sizes/coordinates, never a secret. The hub assembles it with the controller's app half.
+	DRRecipe *DRRecipeHostHalf `json:"dr_recipe"`
 }
 
 // HostMetrics is the host block, sourced from proxmox NodeStatus.