Add memory types article, expand blitter cookbook, update cross-references

New articles:
- 01_hardware/common/memory_types.md: comprehensive Chip/Fast/Slow RAM reference
  with DMA accessibility matrix, per-model configurations (A500-A4000),
  accelerator memory expansion (classic + modern), adaptive software behavior,
  pitfalls with impact analysis, FPGA/emulation notes
- AGENTS.md: documentation standards and methodology guidelines

Blitter programming (08_graphics/blitter_programming.md):
- Rewrote minterm truth table with narrative explanation and worked  example
- Added 7 advanced use cases with assembly/C code: shifted BOB, hardware scroll,
  area fill polygon, interleaved bitplane BOBs, double-buffered game loop,
  GUI window drag, tile map renderer
- Added Good/Bad Patterns section with 5 named antipatterns
- Added Practical Limitations table (10 constraints with workarounds)
- Expanded Common Minterms table with Description and Real-World Use Case columns

Cross-reference updates:
- Root README: added memory types to coverage, quick start, section index
- 01_hardware/README: updated common/ folder description
- address_space.md: linked to memory_types.md and chip_ram_expansion.md
- memory_management.md (exec): linked to hardware memory types reference
- bitmap.md, sprites.md, animation.md, audio.md: linked to memory_types.md
  explaining DMA Chip RAM requirement for each subsystem
- chip_ram_expansion.md: linked to comprehensive memory types article

08_graphics/bitmap.md

@@ -115,3 +115,4 @@ struct BitMap *bm = AllocBitMap(320, 256, 8, BMF_CLEAR | BMF_DISPLAYABLE, NULL);
 - NDK39: `graphics/gfx.h`
 - ADCD 2.1: `AllocBitMap`, `FreeBitMap`, `InitBitMap`
 - HRM: *Amiga Hardware Reference Manual* — bitplane DMA chapter
+- See also: [memory_types.md](../01_hardware/common/memory_types.md) — why bitmaps must be in Chip RAM (DMA accessibility)