fix: address PR review feedback for MIDI 2.0 drivers

Host driver (midi2_host.c):
- midih2_open() now returns actual parsed length instead of max_len,
  preventing composite device interface conflicts
- Parsers (alt0/alt1) refactored to return const uint8_t* end pointer
  following midi_host.c switch/case pattern
- Alt 1 CS Endpoint now parses MIDI 2.0 layout (bNumGrpTrmBlk at
  offset 3 with MIDI_CS_ENDPOINT_GENERAL_2_0 subtype check) instead
  of reusing MIDI 1.0 struct (bNumEmbMIDIJack)
- midih2_set_config() now issues SET_INTERFACE control request via
  tuh_interface_set() before completing configuration. Falls back to
  alt 0 if SET_INTERFACE fails
- Extracted midih2_set_config_complete() and midih2_set_interface_cb()
  for async SET_INTERFACE handling

Device driver (midi2_device.c):
- midi2d_open() skip loop now checks bInterfaceNumber, stopping at
  interfaces that belong to other functions in composite devices
- SET_INTERFACE handler now rejects alt > 1 (returns false/stall)
- Named constants for GTB descriptor types and MIDI protocol values

Descriptor macros (usbd.h):
- TUD_MIDI2_DESC_ALT1_HEAD: iInterface set to 0 (consistent with
  Alt 0), wTotalLength now uses TUD_MIDI2_DESC_ALT1_CS_LEN to cover
  all Alt 1 class-specific descriptors
- TUD_MIDI2_DESC_ALT1_EP: now accepts GTB ID list via variadic args,
  emitting complete CS endpoint descriptor

Host example:
- CMakeLists.txt restricted to rp2040 family (display.c requires
  Pico SDK headers)
- display.c: null terminator after strncpy in log scroll

Documentation:
- class_drivers.rst updated to reflect SET_INTERFACE behavior and
  auto-select with fallback

Addresses: Codex P1 (#1, #2, #3), Copilot (#4-#9)

1 files changed, 4 insertions, 4 deletions

diff --git a/docs/reference/class_drivers.rst b/docs/reference/class_drivers.rst
index 9ed332acb..3ac0d8d4e 100644
--- a/docs/reference/class_drivers.rst
+++ b/docs/reference/class_drivers.rst
@@ -87,7 +87,7 @@ The MIDI 2.0 Host driver enables TinyUSB to enumerate and communicate with USB M
 **Key Features:**
 
 - **Reactive Architecture**: Auto-detects Alt Setting 1 (MIDI 2.0) capability during enumeration
-- **Auto-Selection**: Automatically selects the highest available protocol (MIDI 2.0 preferred)
+- **Auto-Selection**: Automatically selects the highest available protocol and issues SET_INTERFACE to activate Alt Setting 1 when MIDI 2.0 is detected
 - **Transparent Stream Messages**: All data (UMP packets + Stream Messages) flow through callbacks
 - **Memory Safe**: No dynamic allocation, fixed-size instances per device
 
@@ -271,9 +271,9 @@ Architecture
 The MIDI 2.0 Host driver uses a **reactive, callback-driven architecture** that mirrors the proven patterns in TinyUSB's existing device drivers (CDC, HID, etc.):
 
 - **Auto-Detection**: Host automatically detects Alt Setting 1 capability
-- **Auto-Selection**: Selects highest protocol available (MIDI 2.0 preferred)
-- **Application Control**: App makes protocol behavior decisions via callbacks
-- **Transparent I/O**: Stream Messages and UMP packets flow transparently
+- **Auto-Selection**: Selects highest protocol available and issues SET_INTERFACE
+- **Transparent I/O**: Stream Messages and UMP packets flow through callbacks
+- **Callback-Driven**: App receives events via callbacks (descriptor, mount, rx, tx, unmount)
 
 Differences from MIDI 1.0 Host
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^