Address review: HC bit 10 for OP half-line detection, clarify byte switch

- Set bit 10 (0x0400) on HC during odd halflines so the Object
  Processor's CONDITION_SECOND_HALF_LINE branch works correctly.
  This mirrors VC's field bit 11 pattern.
- Use full addresses in JERRYReadByte switch cases to match the
  word read style and avoid confusion about the mask behavior.

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: JoeMatt

src/jerry.c

@@ -388,13 +388,13 @@ uint8_t JERRYReadByte(uint32_t offset, uint32_t who/*=UNKNOWN*/)
    {
       uint16_t value;
 
-      switch (offset & 0xFE)
+      switch (offset & 0xFFFFFFFE)
       {
-         case 0x36: value = JERRYPIT1Prescaler; break;
-         case 0x38: value = JERRYPIT1Divider;   break;
-         case 0x3A: value = JERRYPIT2Prescaler; break;
-         case 0x3C: value = JERRYPIT2Divider;   break;
-         default:   value = 0;                  break;
+         case 0xF10036: value = JERRYPIT1Prescaler; break;
+         case 0xF10038: value = JERRYPIT1Divider;   break;
+         case 0xF1003A: value = JERRYPIT2Prescaler; break;
+         case 0xF1003C: value = JERRYPIT2Divider;   break;
+         default:       value = 0;                  break;
       }
 
       return (offset & 0x01) ? (value & 0xFF) : (value >> 8);

src/tom.c

@@ -737,12 +737,11 @@ void TOMExecHalfline(uint16_t halfline, bool render)
    halfline &= 0x07FF;
 
    // Update HC to approximate position within the scanline.
-   // Even halflines = start of scanline (HC near 0),
-   // odd halflines = midpoint of scanline (HC near HP/2).
-   // This is not cycle-accurate but gives the OP and games a
-   // meaningful value instead of the previous rand() stub.
+   // Bit 10 (0x0400) is the half-line indicator, analogous to VC's
+   // field bit 11. The OP tests this via CONDITION_SECOND_HALF_LINE.
+   // Bits 0-9 approximate the position within the half-line.
    if (halfline & 0x01)
-      SET16(tomRam8, HC, (hp > 0 ? (hp + 1) / 2 : 0));
+      SET16(tomRam8, HC, 0x0400 | (hp > 0 ? (hp + 1) / 2 : 0));
    else
       SET16(tomRam8, HC, 0);