fix(i2c): increase vector_table_size_bytes to 1280 to accommodate IRQ and WaitGroup objects

Commit 6ca6be4 added I2C2_IRQ and WG IPC objects to i2c/system.json5 but did
not update vector_table_size_bytes. The annotations sections overflowed the
0x4A0 (1184 byte) allocation causing a linker overlap error. Bumped to
0x500 (1280 bytes) matching i2c-slave/system.json5 which was correctly
updated in the same commit.
diff --git a/target/ast1060-evb/i2c/system.json5 b/target/ast1060-evb/i2c/system.json5
index 8a20b2d..6f79426 100644
--- a/target/ast1060-evb/i2c/system.json5
+++ b/target/ast1060-evb/i2c/system.json5
@@ -5,8 +5,8 @@
 // 768KB SRAM (640KB usable), executes from RAM
 //
 // Memory Layout (PMSAv7-friendly, power-of-2 aligned regions):
-//   0x00000000 - 0x000004A0: Vector table + kernel annotations (1184 bytes)
-//   0x000004A0 - 0x00020000: Kernel code (~126KB)
+//   0x00000000 - 0x00000500: Vector table + kernel annotations (1280 bytes)
+//   0x00000500 - 0x00020000: Kernel code (~126KB)
 //   0x00020000 - 0x00060000: App flash (256KB: 2 apps × 128KB)
 //   0x00060000 - 0x00080000: Kernel RAM (128KB)
 //   0x00080000 - 0x000A0000: App RAM (128KB: 2 apps × 64KB)
@@ -16,11 +16,11 @@
     arch: {
         type: "armv7m",
         vector_table_start_address: 0x00000000,
-        vector_table_size_bytes: 1184,  // 0x4A0 (272 vectors + thread/stack annotations)
+        vector_table_size_bytes: 1280,  // 0x500 (272 vectors + thread/stack/process annotations)
     },
     kernel: {
-        flash_start_address: 0x000004A0,  // After vector table + annotations
-        flash_size_bytes: 129888,         // ~126KB (ends at 0x00020000, power-of-2 boundary)
+        flash_start_address: 0x00000500,  // After vector table + annotations
+        flash_size_bytes: 129792,         // ~126KB (ends at 0x00020000, power-of-2 boundary)
         ram_start_address: 0x00060000,    // After all flash regions
         ram_size_bytes: 131072,           // 128KB
     },