fix(abc/elixir): elixir_inspect_container is never executed

[dekobon]

Summary

src/metrics/abc/elixir.rs's elixir_inspect_container — the whole peel
loop, roughly lines 49–75 — is never executed. cargo llvm-cov over the
full suite (5,766 tests, --all-features --workspace) records 0 hits on
every line of it, and the file sits at 78.34% region coverage against a
95.61% project figure, almost entirely because of this block.

Evidence

   49|      0|            && node.child(0).is_some_and(|c| c.kind_id() == E::BANG as u16);
   54|      0|        if !has_boolean_content && is_not {
   61|      0|        let next = if is_not {
   66|      0|        let Some(child) = next else { break };
   70|      0|        if matches!(node_kind, elixir_bool_terminal_kinds!()) {
   72|      0|                *conditions += 1.;

This is pre-existing, not introduced by the 2026-09-14 batch:
elixir_inspect_container is on main at line 32 and that batch's hunks
land at lines 10, 108, 191 and 225.

Why it matters

Dead code in a condition-classification path is one of two things, and they
need different fixes:

1. Unreachable — no caller routes an Elixir wrapper here, so an Elixir
   if (!x) / if ((x)) predicate silently scores nothing. That is a live
   metric defect of the class fix(metrics): six ABC and cyclomatic fixes #1459 / fix(abc/groovy): indexing and safe navigation score no condition #1466 / fix(abc/csharp): the null-forgiving b! scores no condition #1463 each fixed in another
   language.
2. Merely untested — reachable but no fixture exercises it, in which
   case it is an untested branch in a metric everyone gates on.

Sibling languages route these through a <lang>_wrapper_operand peel that
their <lang>_count_condition queries. Elixir's equivalent appears not to
be wired to anything.

Suggested first step

Determine which of the two it is before planning a fix: enumerate callers of
elixir_inspect_container, then measure if (!x) / if ((x)) /
if (!(x)) in Elixir against a bare identifier control at the same
cyclomatic, per the measurement discipline in #1458.