docs(amiga): complete AmigaOS 3.1/3.2 developer reference — 172 files across 17 sections

Comprehensive technical documentation covering:
- Hardware: OCS/ECS/AGA custom chip registers, Copper & Blitter deep dives
- Boot sequence: cold boot through startup-sequence
- Binary format: HUNK executable spec, relocation, debug info
- Linking & ABI: .fd files, LVO tables, register calling conventions
- Exec kernel: tasks, interrupts, memory, signals, semaphores
- AmigaDOS: file I/O, FFS/OFS layout, CLI/Shell scripting
- Graphics: planar bitmaps, Copper programming, HAM/EHB modes
- Intuition: screens, windows, IDCMP, BOOPSI
- Devices: trackdisk, SCSI, serial, timer, audio, keyboard
- Libraries: utility, expansion, IFFParse, locale, ARexx
- Networking: bsdsocket API, SANA-II, TCP/IP stack comparison
- Toolchain: GCC, vasm/vlink, SAS/C, NDK, debugging
- Reverse engineering: IDA/Ghidra setup, compiler fingerprints, case studies
- CPU & MMU: 68040/060 emulation libs, PMMU, cache management
- Driver development: SANA-II, Picasso96/RTG, AHI audio

All files include breadcrumb navigation. No local paths or proprietary content.

08_graphics/display_modes.md

@@ -0,0 +1,74 @@
+[← Home](../README.md) · [Graphics](README.md)
+
+# Display Modes — Display Database, ModeID, Monitor Specs
+
+## Overview
+
+OS 3.0+ provides a **display database** that abstracts monitor/chipset capabilities. Applications query available modes by `ModeID` rather than hardcoding `HIRES`/`LACE` flags.
+
+---
+
+## ModeID Format
+
+A ModeID is a ULONG:
+```
+bits 31–16: Monitor ID
+bits 15–0:  Mode within that monitor
+```
+
+| ModeID | Name | Resolution |
+|---|---|---|
+| `$00000000` | LORES | 320×256 (PAL) / 320×200 (NTSC) |
+| `$00008000` | HIRES | 640×256/200 |
+| `$00000004` | LORES-LACE | 320×512/400 |
+| `$00008004` | HIRES-LACE | 640×512/400 |
+| `$00080000` | SUPERHIRES | 1280×256 (ECS+) |
+| `$00080004` | SUPERHIRES-LACE | 1280×512 |
+| `$00039000` | DBLPAL-LORES | 320×256 (AGA scan-doubled) |
+| `$00039004` | DBLPAL-HIRES | 640×256 (AGA) |
+| `$00011000` | DBLNTSC-LORES | 320×200 (AGA) |
+
+---
+
+## Querying the Display Database
+
+```c
+/* graphics.library 39+ */
+ULONG modeID = INVALID_ID;
+struct DisplayInfo di;
+struct DimensionInfo dims;
+
+while ((modeID = NextDisplayInfo(modeID)) != INVALID_ID) {
+    if (GetDisplayInfoData(NULL, (UBYTE *)&di, sizeof(di),
+                           DTAG_DISP, modeID)) {
+        if (GetDisplayInfoData(NULL, (UBYTE *)&dims, sizeof(dims),
+                               DTAG_DIMS, modeID)) {
+            Printf("ModeID $%08lx: %ldx%ld, %ld colours\n",
+                    modeID,
+                    dims.Nominal.MaxX - dims.Nominal.MinX + 1,
+                    dims.Nominal.MaxY - dims.Nominal.MinY + 1,
+                    1 << di.NotAvailable ? 0 : dims.MaxDepth);
+        }
+    }
+}
+```
+
+---
+
+## Best Mode Selection
+
+```c
+ULONG bestMode = BestModeIDA((struct TagItem[]){
+    { BIDTAG_NominalWidth,  640 },
+    { BIDTAG_NominalHeight, 480 },
+    { BIDTAG_Depth,         8 },
+    { TAG_DONE, 0 }
+});
+```
+
+---
+
+## References
+
+- NDK39: `graphics/displayinfo.h`, `graphics/modeid.h`
+- ADCD 2.1: `NextDisplayInfo`, `GetDisplayInfoData`, `BestModeIDA`