Implement NUFLI delta encoding with scanlines

- Add tools/apply_scanlines.py for CRT scanline effect
- Add tools/nufli_delta.py for delta encoding (base + bitmask deltas)
- Delta format: 2880 byte bitmask + N byte values per screen
- 40.1% size reduction vs raw NUFLI (69KB vs 115KB for 5 screens)
- Base (23KB) at 000-FFF, title delta (7KB) at -
- Other deltas use title as fallback (TODO: disk loading)
- Update tasks.md with scanline and delta encoding documentation

src/main.c

@@ -13,13 +13,6 @@
 //                            and calls game_step() once per frame.
 //   6. while (1) {}         — idle.  All per-frame work happens in
 //                            the IRQ handler.
-//
-// In Phase 4 step 6 was `while (1) game_step();` — a busy-wait that
-// called game_step as fast as the CPU could, so the "frame counter"
-// was CPU-bound.  In Phase 5 the busy-wait is gone: game_step is
-// called from the raster IRQ at exactly 50 Hz, so state durations
-// are wall-clock-bound (60 frames = 1.2 sec, etc.) regardless of
-// what the CPU is doing between IRQs.
 
 #include "memmap.h"
 #include "audio.h"
@@ -27,18 +20,6 @@
 #include "score.h"
 #include "tick.h"
 
-// We don't malloc, so the heap is unused.  Setting it to 0 frees the
-// space for the screen data in the main region.
-//
-// The stack is set to 0x400 (1 KB) — this is the oscar64 default,
-// pinned explicitly so the layout is predictable across `-O1` /
-// `-O3` builds.  With `-O3` the code section is larger, so the
-// data section's spillover into the default stack/heap gap region
-// leaves only ~0x400 for both.  Anything larger (0x600+) makes
-// `-O3` fail to link with "Cannot place stack section".  1 KB is
-// plenty because the oscar64 software stack lives in zero-page
-// (0xF7-0xFF, 9 bytes per the -O3 default); the spillover area
-// only needs to hold the few locals/params that don't fit in ZP.
 #pragma heapsize(0)
 #pragma stacksize(0x400)
 
@@ -50,8 +31,7 @@ int main(void)
 	game_init();
 	rasterirq_setup();
 
-	// The raster IRQ does all the per-frame work.  The main loop
-	// is a deliberate spin: nothing to do between IRQs.
+	// The raster IRQ does all the per-frame work.
 	for (;;)
 		;