Add complex-app example: loops, pointers, structs, bit shifts/masks

[Copilot]

Adds examples/complex-app/ — a richer ARM VM example alongside the existing simple-app, covering the full range of typical embedded/systems code patterns.

New files

• input.c — C source with three internal functions plus main:
  • compute_flags(value, shift, mask) — register-controlled shift + AND mask
  • sum_array(arr*, count) — counted loop over a pointer/array
  • process_record(record*) — struct-like field access via pointer offsets + bitwise OR
• complex.s — hand-written ARMv7 assembly (Apple/ARM UAL syntax); pre-generated so it runs on Linux without a cross-compiler
• main.c — host registering print_int and print_string via avm_register()
• Makefile — make run uses the checked-in assembly; make all regenerates from input.c on macOS with Xcode

Assembly highlights

@ Register-controlled bit shift + mask
_compute_flags:
    mov r0, r0, lsl r1      @ value << shift
    and r0, r0, r2          @ & mask
    bx lr

@ Loop with scaled-register array indexing
_sum_loop:
    cmp r4, r1
    bge _sum_done
    ldr r2, [r0, r4, lsl #2]   @ arr[i] = *(arr + i*4)
    add r5, r5, r2
    add r4, r4, #1
    b _sum_loop

@ Struct-like field access via immediate offsets
_process_record:
    ldr r1, [r0, #4]        @ record[1] (value)
    ldr r2, [r0, #8]        @ record[2] (flags)
    mov r2, r2, lsl #8
    orr r0, r1, r2
    bx lr

Expected output

Running complex ARM32 program...
compute_flags result: 3840
sum_array result:     150
process_record result: 1834
Program returned: 150

[corepunch]

@copilot Add also structs in app and pointers to functions in those structs