fix(pure-magic): apply binary/text test gate at rule entry only

[tnaroska]

Summary

Fix a binary/text gating bug that silently stripped any rule whose message lives on a scalar/float/pstring/string16/indirect child — most visibly magdir/rtf, which carries its message on a level-2 ubyte qualifier and was reported as plain ASCII text instead of Rich Text Format data.

Problem

Match::matches (pure-magic/src/lib.rs) skipped tests with is_only_binary / is_only_text mismatching the stream kind on every recursion. Once the top-level string {\rtf matched on a text-classified stream, its >5 ubyte and >>5 ubyte children were dropped because ubyte is binary-only — so the rule's message (carried on the level-2 child) never fired.

Fix

Hoist the gate into EntryNode::matches and run it only when self.root. This mirrors upstream libmagic match() in src/softmagic.c:243-262, where the STRING_BINTEST / STRING_TEXTTEST check fires inside the top-level for (magindex = 0; ...) loop and goto flush skips sub-tests — i.e. the binary/text decision is taken once at the outer match loop, not re-applied to children. Top-level perf filtering across the >300 rule files is preserved.

Tests

Two regression tests in pure-magic/src/lib.rs:

• test_string_parent_with_scalar_children_on_text_stream — RTF-shaped rule emits its message on a text stream (the bug).
• test_rtf_droid_skip_still_rejects — the upstream level-1 >5 ubyte !0xAB qualifier (added specifically to skip DROID fmt-355-signature-id-522.rtf) still rejects that input now that children run on text streams.

Test plan

• cargo test -p pure-magic — passes locally (139 tests).
• Maintainer review.

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