Stop pointer parameters leaking value-pool slots

Create structure parameters before allocating their representation, then keep pointer references in the call variable's inline slot. Add an 8,000-call regression and document the remaining by-value structure escape limitation.

Co-authored-by: andrew <andrew@aklabs.net>
Co-authored-by: OpenAI Codex (GPT-5) <noreply@openai.com>

docs/14-architecture.md

@@ -380,8 +380,10 @@ no free, so anything drawn from it is spent for the life of the run — and scop
 returns a variable's *slot* without returning its storage. A scalar therefore does not
 draw from it at all: `akbasic_variable_init()` points a one-element non-`@` variable at
 its own `inlinevalue`, which is what makes a local, a `FOR` counter and a `DEF` parameter
-free. Arrays and structures still spend, deliberately, because a pointer into a record is
-allowed to outlive the scope that DIMmed it.
+free. A pointer parameter is also free: it owns only its one-slot reference, so its
+`inlinevalue` dies with the call while the target remains in the caller's storage. Arrays,
+structures and by-value structure parameters still spend, deliberately, because a pointer
+into a record is allowed to outlive the scope that DIMmed it.
 [Chapter 13](13-differences.md) states the same budget from a BASIC programmer's side.
 
 The per-environment three are reset at the top of every line, which is what makes