[AjayBrahmakshatriya]

Fixes #118.

Summary

for_loop_finder could move an update expression into a generated for
header while leaving variables referenced by that expression declared
inside the loop body. This produced invalid generated code.

For example:

while (i < n) {
    dyn_var<int> one = 1;
    i = i + one;
}

could generate:

  for (...; i < n; i = i + one) {
      int one = 1;
  }

Changes

• Find loop-body declarations referenced by an extracted update.

• Hoist those declarations to the scope immediately surrounding the
  generated for.

• Replace their original declarations with assignments, preserving the
  original initialization timing and side effects.

• Apply the same behavior recursively for nested loops.

• Keep the original while when a declaration cannot safely be split,
  including references, arrays, function types, top-level const, and
  nonautomatic declarations.

• Require fallthrough and explicit-continue updates to be structurally
  equivalent before extracting them.

• Correct validation of update statements preceding continue.

• Add sample66 coverage for:

  • A simple loop.
  • Nested loops.
  • A loop containing an early return.

• Add golden outputs for normal and recovered-variable-name modes.

Validation

• Built and ran sample66 in both extraction modes.

• Verified both generated outputs against their golden files.

• Verified the default output with GCC C11 syntax checking.

• Tested updates containing multiple body-local variables and external
  variables.

• Tested recursive hoisting through nested loops.

• Confirmed differing branch updates remain represented as a while.

• Confirmed all 63 existing golden-tested samples remain unchanged.

• Ran formatting and git diff --check.