chore: help record types and one prototype header per folder

docs/game/help-messages.md

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+# Help messages and tutorial records
+
+`HelpState` in `rnc/ui/help/help_state.h` is the shared boot help-window
+layout. Its geometry comes from `link_localized_display_text` and is consumed
+by `draw_help`: `half_width`/`half_height` are the target size, while
+`frame_half_width`/`frame_half_height` describe the animated frame.
+
+## Message fields
+
+`msg` indexes the loaded message table; `pending` is a request ID, with -1
+meaning no request. `entry` indexes persistent records, and `count` bounds
+the loaded table. These are different index spaces.
+
+A `HelpMessageEntry` is 16 bytes on EE. Its first word is a text pointer
+after relocation; archive loaders retain their integer-offset view before
+relocation. `find_help_message_index` compares `message_id` at 0x04.
+`update_help_state` adds 30000 to `audio_track_offset` at 0x08 for the
+secondary audio stream, with -1 meaning no audio. The final word remains
+unknown. Message IDs and audio-track offsets are not interchangeable.
+
+## Records and time
+
+`HelpRecord` and `UsageStat` are 8-byte records: a 16-bit count, a 16-bit
+`latest_time_bucket`, and 32-bit level/status flags. Writers retain the
+maximum of `scale_game_frames(play_time) / 600`; readers multiply by 600
+when testing elapsed time. This is a coarse play-time bucket, not a best
+score or countdown. Original narrowing and comparisons are preserved.
+
+`UsageStat.level_mask` is signed: Novalis and Kerwan test it against zero
+to inspect bit 31. `HelpRecord.level_flags` remains unsigned. Visited-level
+bits coexist with bit 31, which `clear_help_record_high_bits` clears, so
+it is not an immutable "ever shown" flag. `help_request` rejects a count
+of 0xFFFF; other writers saturate the count there.
+
+## Reference evidence
+
+RC1 functions and callers establish these meanings. `rac1-decomp` at
+`05da3217a4046ac01dec3ac74f051a348f063155` corroborates geometry and request
+offsets in `src/game/help.c` and `src/overlays/shared/help_00203E98.c`.
+Its help-update code derives from Lombyte and is not independent evidence.
+No PAL addresses or implementation bodies were imported.
+
+The help window and record layout checks in `src/check/` verify EE offsets
+and sizes; boot and overlay byte checks remain the acceptance gates.

include/rnc/audio.h

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+#ifndef LOMBYTE_RNC_AUDIO_H
+#define LOMBYTE_RNC_AUDIO_H
+
+#include "types.h"
+
+s32 snd_start_sound_system(void) __asm__("FUN_0012da28");
+
+#endif /* LOMBYTE_RNC_AUDIO_H */

include/rnc/audio/decoder.h

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+#ifndef LOMBYTE_RNC_AUDIO_DECODER_H
+#define LOMBYTE_RNC_AUDIO_DECODER_H
+
+#include "types.h"
+
+struct AudioDec;
+
+s32  audio_dec_create(struct AudioDec *, s32, s32, s32) __asm__("FUN_0023abd0");
+int  audio_dec_is_preset(struct AudioDec *) __asm__("func_0023AEE0");
+void audio_dec_reset(struct AudioDec *) __asm__("FUN_0023ad10");
+
+#endif /* LOMBYTE_RNC_AUDIO_DECODER_H */

include/rnc/audio/effects.h

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+#ifndef LOMBYTE_RNC_AUDIO_EFFECTS_H
+#define LOMBYTE_RNC_AUDIO_EFFECTS_H
+
+#include "types.h"
+
+void snd_auto_reverb(s32, s32, s32, s32) __asm__("FUN_0012efe0");
+void snd_pre_alloc_reverb_work_area(s32, s32) __asm__("FUN_0012efa8");
+
+#endif /* LOMBYTE_RNC_AUDIO_EFFECTS_H */

include/rnc/audio/mixer.h

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+#ifndef LOMBYTE_RNC_AUDIO_MIXER_H
+#define LOMBYTE_RNC_AUDIO_MIXER_H
+
+#include "types.h"
+
+void snd_set_group_voice_range(s32, s32, s32) __asm__("FUN_0012e2b8");
+void snd_set_mixer_mode(s32, s32) __asm__("FUN_0012e280");
+
+#endif /* LOMBYTE_RNC_AUDIO_MIXER_H */

include/rnc/audio/movie.h

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+#ifndef LOMBYTE_RNC_AUDIO_MOVIE_H
+#define LOMBYTE_RNC_AUDIO_MOVIE_H
+
+#include "types.h"
+
+void snd_close_movie_sound(void) __asm__("FUN_0012f0e0");
+void snd_update_movie_adpcm(s32, s32) __asm__("FUN_0012f148");
+
+#endif /* LOMBYTE_RNC_AUDIO_MOVIE_H */

include/rnc/audio/music.h

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+#ifndef LOMBYTE_RNC_AUDIO_MUSIC_H
+#define LOMBYTE_RNC_AUDIO_MUSIC_H
+
+#include "types.h"
+
+void music_pause(s32);
+void music_start_track(s32, s32, s32) __asm__("FUN_00215c40");
+void music_start_track_10000(s32, s32, s32) __asm__("FUN_002158a0");
+void music_start_track_20000(s32, s32, s32) __asm__("FUN_002157d0");
+void music_start_track_30000(s32, s32, s32) __asm__("FUN_002156d8");
+void music_start_track_40000(s32, s32, s32) __asm__("FUN_00215600");
+void music_start_track_50000(s32, s32, s32) __asm__("FUN_00215518");
+void music_start_track_60000(s32, s32, s32) __asm__("FUN_00215440");
+void music_update(void) __asm__("FUN_00216290");
+void reset_music(void) __asm__("FUN_00215390");
+
+#endif /* LOMBYTE_RNC_AUDIO_MUSIC_H */

include/rnc/audio/rpc.h

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+#ifndef LOMBYTE_RNC_AUDIO_RPC_H
+#define LOMBYTE_RNC_AUDIO_RPC_H
+
+#include "types.h"
+
+void snd_prepare_return_buffer(s32 *, s32);
+s32  snd_send_iop_command_and_wait(s32, s32, u8 *) __asm__("FUN_0012e548");
+void snd_send_iop_command_no_wait(s32, s32, u8 *, s32, s64) __asm__("FUN_0012e6e0");
+
+#endif /* LOMBYTE_RNC_AUDIO_RPC_H */

include/rnc/audio/sound.h

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+#ifndef LOMBYTE_RNC_AUDIO_SOUND_H
+#define LOMBYTE_RNC_AUDIO_SOUND_H
+
+#include "rnc/audio/voice_pool.h"
+#include "types.h"
+
+struct VoiceVolumeDefinition;
+
+s32  calculate_voice_distance_volume(struct VoiceVolumeDefinition *,
+                                     f32,
+                                     f32,
+                                     f32) __asm__("FUN_0022c6f8");
+s32  calculate_voice_pan(s32, f32 *, void *) __asm__("FUN_0022c830");
+void clamp_voice_position_to_collision(s32) __asm__("FUN_0022c5a8");
+void initialize_gameplay_sound_system(void) __asm__("FUN_0022c8d0");
+int  snd_get_doppler_pitch_mod(int);
+void store_sound_bank_handle_callback(int, long) __asm__("FUN_0022dd78");
+int  test_voice_occlusion(VoiceSlot *, void *) __asm__("FUN_0022c658");
+void voice_start_callback(int, long) __asm__("FUN_0022dd90");
+void voice_update_callback(int, long) __asm__("FUN_0022ddd8");
+
+#endif /* LOMBYTE_RNC_AUDIO_SOUND_H */