device-manager: data-driven driver matching via /etc/devices.csv

Replace the three hardcoded switch tables (pciDriverForIdentity, hidDriverFor,
usbDriverForIdentity) with an authoritative, human-readable device registry the
manager reads at boot. Matching is most-specific-wins across
base/subclass/prog_if/vendor/device/subsystem/hid, so a precise vendor:device
rule and a generic class rule coexist; an unmatched device is logged, never
guessed. This resolves docs' "matching stays code until the third bus".

- ABI: child_added and DeviceDescriptor gain vendor/device/subsystem; child_added
  gains a bus discriminator (BusKind) so PCI and USB class triples match against
  the right namespace.
- pci-bus reads vendor/device (config 0x00) and subsystem (0x2C, type-0) and
  reports them.
- library/device/registry: freestanding CSV parser + matchDriver() with
  specificity scoring; 5 unit tests wired into `zig build test`.
- etc/devices.csv bundled into the initrd; the kernel serves /etc directly, so
  the manager reads it before any filesystem service is up (fat starts later).
- virtio-gpu: drop the now-redundant post-spawn 1AF4:1050 re-confirm, since the
  registry binds this driver by exact identity.
- Remove the orphaned system/drivers/display driver (unreferenced by build or
  registry).
- docs: new devices-csv.md; device-manager.md "matching stays code" resolved.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KJqSiLLchDUUCoXn5jsiwd

system/drivers/pci-bus/pci-bus.zig

@@ -153,6 +153,12 @@ fn registerAndReport(bus: u64, dev: u64, function: u64, class_triple: u32) void
     var descriptor = std.mem.zeroes(device.DeviceDescriptor);
     descriptor.class = @intFromEnum(device.DeviceClass.pci_device);
     descriptor.pci_class = class_triple;
+    // Vendor/device from the first config dword (0x00): low half vendor, high half
+    // device. These carry to the manager's /etc/devices.csv matcher so a function
+    // can bind on its exact 1AF4:1050 identity, not just its class triple.
+    const vendor_device = configRead(bus, dev, function, 0x00);
+    descriptor.vendor = @truncate(vendor_device);
+    descriptor.device = @truncate(vendor_device >> 16);
     descriptor.resources[0] = .{
         .kind = @intFromEnum(device.ResourceKind.memory),
         .start = ecam_physical + (((bus - start_bus) << 20) | (dev << 15) | (function << 12)),
@@ -164,6 +170,11 @@ fn registerAndReport(bus: u64, dev: u64, function: u64, class_triple: u32) void
     // write all-ones, read the writable mask back, restore. Header type 0 only.
     const header_type = (configRead(bus, dev, function, 0x0C) >> 16) & 0x7F;
     if (header_type == 0) {
+        // Subsystem id lives at 0x2C only on type-0 (device) headers, not on
+        // bridges: dword low half is subsystem-vendor, high half subsystem-device.
+        // Repack vendor-first so it reads like the CSV's `ssvid:ssid`.
+        const subsystem_dword = configRead(bus, dev, function, 0x2C);
+        descriptor.subsystem = (@as(u32, @truncate(subsystem_dword)) << 16) | @as(u32, @truncate(subsystem_dword >> 16));
         const command = configRead16(bus, dev, function, 0x04);
         configWrite16(bus, dev, function, 0x04, command & ~@as(u16, 0b11));
         var i: u64 = 0;
@@ -215,10 +226,14 @@ fn registerAndReport(bus: u64, dev: u64, function: u64, class_triple: u32) void
         return;
     };
     const report = device_manager_protocol.ChildAdded{
+        .bus = @intFromEnum(device_manager_protocol.BusKind.pci),
         .parent = bridge_id,
         .bus_address = (bus << 8) | (dev << 3) | function,
         .identity = class_triple,
         .device_id = registered,
+        .vendor = descriptor.vendor,
+        .device = descriptor.device,
+        .subsystem = descriptor.subsystem,
     };
     var reply: [device_manager_protocol.message_maximum]u8 = undefined;
     _ = ipc.call(manager_handle, std.mem.asBytes(&report), &reply) catch {