establishment: block stops being a name, and enumerate learns to page

P2 of docs/establishment-planes-plan.md. usb-storage serves nameless — one
process per stick cannot share an exclusive bind, and a second stick used to
die silently on -EBUSY before ever helloing. Its one hello now moves both
directions at once: the block-serving endpoint up, its controller channel
down. fat finds its volume through the manager — a new `.consumer` role asks
for the channel of the driver BOUND TO a device (distinct from the device's
reporter), found by enumerating the tree for the mass-storage identity.
fat stays single-volume; the boot-volume-by-content choice is M21.

The conversion immediately caught a live truncation of exactly the audit's
shape: ChildEntry grew to 32 bytes, one enumerate reply holds ~7, and a real
tree carries a dozen ACPI nodes before the first USB child — the storage
entry silently never fit (the protocol comment already said "paging joins
the protocol if a tree ever outgrows one packet"). enumerate is now paged:
Header.target is the start cursor, a short page is the end; device-list's
page-0 read is unchanged.

Grant rows move with the code: the block bind and fat's block open die, fat
gains open device-manager. Gate: 18 cases green including the registry
trio, device-list, and both IOMMU storage variants.

system/drivers/usb-hid/keyboard.zig

@@ -77,7 +77,7 @@ pub fn main(init: process.Init) void {
 
     // The hello both meets the spawn deadline and brings back the channel to
     // THIS device's controller — routed by lineage, never found by name.
-    const bus = device_manager.helloForChannel(.device, device_id) orelse return;
+    const bus = device_manager.helloForChannel(.device, device_id, null) orelse return;
     var device = usb.open(bus, device_id) orelse {
         std.log.info("could not open device {d}", .{device_id});
         return;

system/drivers/usb-hid/mouse.zig

@@ -43,7 +43,7 @@ pub fn main(init: process.Init) void {
 
     // The hello both meets the spawn deadline and brings back the channel to
     // THIS device's controller — routed by lineage, never found by name.
-    const bus = device_manager.helloForChannel(.device, device_id) orelse return;
+    const bus = device_manager.helloForChannel(.device, device_id, null) orelse return;
     var device = usb.open(bus, device_id) orelse {
         std.log.info("could not open device {d}", .{device_id});
         return;

system/drivers/usb-storage/usb-storage.zig

@@ -82,10 +82,13 @@ fn transact(cdb: []const u8, direction_in: bool, data_physical: u64, data_length
 var bring_up_failed = false;
 
 fn initialise(endpoint: ipc.Handle) bool {
-    _ = endpoint;
-    // The hello both meets the spawn deadline and brings back the channel to
-    // THIS device's controller — routed by lineage, never found by name.
-    const bus = device_manager.helloForChannel(.device, device_id) orelse return false;
+    // One hello, both directions: the block-serving endpoint goes UP (the
+    // manager routes fat's consumer hello here — this driver serves one
+    // volume, one process per stick, so `block` is never a registry name),
+    // and the channel to THIS device's controller comes DOWN, routed by
+    // lineage. A second stick used to die silently on the exclusive bind;
+    // now every instance is reachable through its lineage.
+    const bus = device_manager.helloForChannel(.device, device_id, endpoint) orelse return false;
     device = usb.open(bus, device_id) orelse {
         std.log.info("could not open device {d}", .{device_id});
         return false;
@@ -224,8 +227,10 @@ pub fn main(init: process.Init) void {
         std.log.info("malformed device id '{s}'", .{argument});
         return;
     };
+    // No `.service` name: several instances provide the block contract (one
+    // per stick), so consumers are routed here by the device manager's
+    // lineage, never by a registry bind — the endpoint goes up in the hello.
     service.run(block_protocol.message_maximum, .{
-        .service = "block",
         .init = initialise,
         .on_message = onMessage,
     });