docs(amiga): make cross-references clickable markdown links

Convert bare .md path references in 29 files to proper [name](relative/path)
markdown links for GitHub navigation.

01_hardware/aga_a1200_a4000/aga_copper.md

@@ -366,6 +366,6 @@ AGA has 256 colours but still only 32 colour registers visible at a time. To loa
 ## References
 
 - HRM: *Copper* chapter — authoritative register descriptions
-- `08_graphics/copper.md` — graphics.library UCopList API
-- `08_graphics/copper_programming.md` — additional examples
-- `01_hardware/ocs_a500/copper.md` — OCS-level register reference
+- [copper.md](../../08_graphics/copper.md) — graphics.library UCopList API
+- [copper_programming.md](../../08_graphics/copper_programming.md) — additional examples
+- [copper.md](../ocs_a500/copper.md) — OCS-level register reference

01_hardware/aga_a1200_a4000/aga_registers_delta.md

@@ -6,7 +6,7 @@
 
 ### FMODE — $DFF1FC (AGA only)
 
-DMA fetch mode — see `chipset_aga.md` for full description.
+DMA fetch mode — see [chipset_aga.md](chipset_aga.md) for full description.
 
 ### BPLCON4 — $DFF10C (AGA only)
 
@@ -63,7 +63,7 @@ bit 3:    BRDSPRT — sprites visible in border
 
 ## AGA-Specific BPLCON0 Bits
 
-See `chipset_aga.md` — bit 4 is the MSB of the bitplane count for 7/8-plane modes.
+See [chipset_aga.md](chipset_aga.md) — bit 4 is the MSB of the bitplane count for 7/8-plane modes.
 
 ## Colour Register Access — Low Nibble Protocol
 

01_hardware/ecs_a600_a3000/ecs_registers_delta.md

@@ -44,11 +44,11 @@ move.w  #$0A00, $DFF1DC    ; VARBEAMEN + VARVSYEN (31 kHz VGA-like)
 
 ### BPLCON3 — $DFF106 (ECS Denise only)
 
-New bitplane/sprite control register — see `chipset_ecs.md` for full bit definition.
+New bitplane/sprite control register — see [chipset_ecs.md](chipset_ecs.md) for full bit definition.
 
 ### DENISEID — $DFF07C (read only, ECS+)
 
-Chip identification — see `chipset_ecs.md`.
+Chip identification — see [chipset_ecs.md](chipset_ecs.md).
 
 ## Changed / Extended Registers