feat: rebuild heap4 card around upstream FreeRTOS allocator

tests/check_task03_elf.sh

@@ -0,0 +1,15 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+elf="${1:?usage: check_task03_elf.sh ELF [tool-prefix]}"
+prefix="${2:-riscv64-unknown-elf-}"
+nm="${prefix}nm"
+objdump="${prefix}objdump"
+
+test -s "$elf"
+for symbol in pvPortMalloc vPortFree prvInsertBlockIntoFreeList ucHeap \
+              heap4_fragmented_checkpoint task03_debug_checkpoint g_task03_pass; do
+  "$nm" -a "$elf" | grep -E "[[:space:]]${symbol}$" >/dev/null
+done
+"$objdump" -d "$elf" | grep -E 'addi[[:space:]]+sp,sp,-' >/dev/null
+printf 'PASS Task 3 links upstream heap_4 and observable checkpoints: %s\n' "$elf"

tests/test_host.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+root="$(cd -- "$(dirname -- "${BASH_SOURCE[0]}")/.." && pwd)"
+make -C "$root" PROFILE=observe host >/dev/null
+
+check_output() {
+  local program="$1" expected="$2" actual
+  actual="$($program)"
+  if [[ "$actual" != "$expected" ]]; then
+    printf 'FAIL %s\nexpected: %s\nactual:   %s\n' "$program" "$expected" "$actual" >&2
+    return 1
+  fi
+  printf 'PASS %s: %s\n' "$(basename -- "$(dirname -- "$program")")" "$actual"
+}
+
+check_output "$root/host-build/task01_first_fit_split/prog" \
+  'header=16 wanted=32 remainder=224 payload=16 aligned=1 pass=1'
+check_output "$root/host-build/task02_address_order_coalesce/prog" \
+  'before_nodes=2 before_total=96 before_largest=48 after_nodes=1 after_total=144 after_largest=144 pass=1'
+check_output "$root/host-build/task03_freertos_heap4/prog" \
+  'initial=4080 after=3952 fragmented=2 final=4080 min=3952 aligned=1 oom=1 hooks=1 asserts=0 pass=1'