runtime: std.log for every user binary — kernel-stamped attribution

library/runtime/log.zig wires std.log to the tagged ring: the root shim
installs std_options for every binary (programs may override), logFn
formats one line per record and emits it with its level via
debug_write — the payload no longer carries the process's name; the
kernel stamps identity structurally and the serial renderer prints the
'<binary path>: ' prefix, so the transcript keeps its shape.

Migrate every writeLine/logLine/log helper family (init, vfs, fat,
device-manager, acpi, pci-bus, ps2-bus x3, usb-hid x2, usb-storage,
usb-xhci-bus, virtio-gpu — 104 call sites) to std.log.info, dropping
the hand-written prefixes. A leveled record is a complete line by
contract (raw emissions may still build lines from pieces). Test
fixtures and the display/input services keep raw writes for now — their
ring records are attributed by the kernel regardless.

Harness regexes follow the renamed prefixes (usb-hid-keyboard,
discovery) and path-named restart lines.

system/services/acpi/acpi.zig

@@ -21,11 +21,6 @@ const power = runtime.power_protocol;
 /// integer decode names the opcodes instead of bare 0x0A/0x0B/… (docs/coding-standards.md).
 const opcodes = aml.opcodes;
 
-fn writeLine(comptime fmt: []const u8, arguments: anytype) void {
-    var line: [128]u8 = undefined;
-    _ = runtime.system.write(std.fmt.bufPrint(&line, fmt, arguments) catch return);
-}
-
 // The claimed acpi-tables node and the resource index of its broad io_port
 // window — the Hal routes every port access through this one claim.
 var node_id: u64 = 0;
@@ -163,12 +158,12 @@ pub fn main(init: runtime.process.Init) void {
     };
     var namespace = result.namespace;
     const devices = aml.deviceCount(&namespace);
-    writeLine("/system/services/acpi: parsed {d} AML blob(s), {d} namespace devices\n", .{ block_count, devices });
+    std.log.info("parsed {d} AML blob(s), {d} namespace devices", .{ block_count, devices });
     if (floor) |minimum| {
         if (devices >= minimum) {
             _ = runtime.system.write("acpi-parse: ok\n");
         } else {
-            writeLine("acpi-parse: too few (ring-3 {d} < floor {d})\n", .{ devices, minimum });
+            std.log.info("acpi-parse: too few (ring-3 {d} < floor {d})", .{ devices, minimum });
         }
         // Self-verify mode is standalone (no manager); stop before reporting.
         while (true) runtime.system.sleep(1000);
@@ -216,9 +211,9 @@ fn onInit(endpoint: runtime.ipc.Handle) bool {
         const hid = entry.hid[0..entry.hid_len];
         const desc = acpi_ids.description(hid);
         if (desc.len != 0)
-            writeLine("/system/services/acpi: reported {s} (device {d}, {d} resources) — {s}\n", .{ hid, entry.device_id, entry.resource_count, desc })
+            std.log.info("reported {s} (device {d}, {d} resources) — {s}", .{ hid, entry.device_id, entry.resource_count, desc })
         else
-            writeLine("/system/services/acpi: reported {s} (device {d}, {d} resources)\n", .{ hid, entry.device_id, entry.resource_count });
+            std.log.info("reported {s} (device {d}, {d} resources)", .{ hid, entry.device_id, entry.resource_count });
         if (manager) |h| {
             var report = protocol.ChildAdded{ .parent = node_id, .bus_address = entry.device_id, .identity = 0, .device_id = entry.device_id };
             @memcpy(report.hid[0..entry.hid_len], entry.hid[0..entry.hid_len]);
@@ -226,7 +221,7 @@ fn onInit(endpoint: runtime.ipc.Handle) bool {
             _ = runtime.ipc.call(h, std.mem.asBytes(&report), &reply) catch {};
         }
     }
-    writeLine("/system/services/acpi: reported {d} device(s) to the manager\n", .{registered_count});
+    std.log.info("reported {d} device(s) to the manager", .{registered_count});
 
     armPowerButton(endpoint);
     return true;
@@ -373,7 +368,7 @@ fn publishNotify(node: *aml.Node, code: u64) void {
     const which: power.Event = if (std.mem.eql(u8, hid[0..7], "PNP0C0A")) .battery else if (std.mem.eql(u8, hid[0..7], "ACPI0003")) .ac else if (std.mem.eql(u8, hid[0..7], "PNP0C0D")) .lid else .notify;
     var event = power.EventMessage{ .event = @intFromEnum(which), .code = @truncate(code) };
     event.hid = hid;
-    writeLine("power: notify {s} code {d}\n", .{ hid[0..7], code });
+    std.log.info("power: notify {s} code {d}", .{ hid[0..7], code });
     publishEvent(std.mem.asBytes(&event));
 }
 
@@ -500,7 +495,7 @@ fn registerDevice(node: *aml.Node, hid: [8]u8, interpreter: *aml.Interpreter) vo
     applyCrs(&descriptor, node, interpreter);
 
     const id = device.register(node_id, &descriptor) orelse {
-        writeLine("/system/services/acpi: register refused for {s}\n", .{hid[0..@intCast(hid_len)]});
+        std.log.info("register refused for {s}", .{hid[0..@intCast(hid_len)]});
         return;
     };
     registered[registered_count] = .{ .hid = hid, .hid_len = @intCast(hid_len), .device_id = id, .resource_count = descriptor.resource_count };