Blank only test items in RT-04 source scanner (#169)

[afflom]

Closes #169

Summary

• Updates without_test_items in crates/conformance/src/cases/runtime.rs so that:
  • #![cfg(test)] blanks the whole file only when it appears as one of the file's leading inner attributes before any item (and never when it appears inside an inline mod m { #![cfg(test)] }).
  • #[cfg(test)] blanks only when, after any further outer attributes (#[...]), optional visibility (pub, pub(...)), and item modifiers, it is followed by an item keyword (mod, fn, use, impl, const, static, struct, enum, union, type, trait, extern, macro_rules!), and never blanks production code after a #[cfg(test)] on a struct field, enum variant, function parameter, or match arm.
  • Also includes the scanner hardening from the fix(#154): the runtime gates read what they claim to #156 review (cr"..." raw C strings, comment-blanked literal gaps in runtime_texts, inline Lean comments/set_option ... in before declaration keywords, and _root_. / guillemets in declares_under_runtime).
• Plants all five non-item #[cfg(test)] / inline #![cfg(test)] shapes and + string concatenation in rt_04, and records the planted defect output in VERIFICATION.md and CHANGELOG.md.
• Touches no files in SEMANTIC_DIRS and changes no diagnostic code or conformance ID.

[afflom]

@afflom @humuhumu33 Ready for review.

• issue-169-rt04-cfg-test (b3a0d981e) contains main (8765feea3).
• Draft rest leg, honesty, and reproducibility passed on b3a0d981e.
• No files in SEMANTIC_DIRS are touched, and no conformance ID or diagnostic code is added or modified.
• All five non-item #[cfg(test)] / inline #![cfg(test)] shapes from [v0.4] RT-04: blank only test items, never the code after a cfg(test) that is not on an item (follow-up to #156) #169 plus + concatenation and the fix(#154): the runtime gates read what they claim to #156 review scanner refinements are planted in rt_04 and recorded in VERIFICATION.md.

[afflom]

@afflom @humuhumu33 Full ready-for-review gate run 39097581738 is 25/25 green (honesty and reproducibility also green: 27/27 checks passed) on b3a0d981e, which contains main (8765feea3) and touches nothing in SEMANTIC_DIRS.

[afflom]

Rebased onto main (193cd2148) at 6a8c5b56d, removing the stray BS-02 CHANGELOG bullet that conflicted with main, and verified cargo xtask validate, conformance_rt_04, and conformance_rp_08 locally. cc @afflom @humuhumu33

[afflom]

@afflom @humuhumu33 Full ready-for-review gate run 39113611038 is 25/25 green (honesty and reproducibility also green: 27/27 checks passed, mergeStateStatus: CLEAN) on 6a8c5b56d, which contains main (193cd2148) and touches nothing in SEMANTIC_DIRS.

[afflom]

Landed through wave 2, #171, merged to main as d51d9f223: this branch's head 1cc1ab1cc (the #169 fix on top of main) is merged into that PR unchanged, so its commit is in main's history and #169 is closed by the merge. Closing this PR by hand; its gate ran as part of #171's run 39125361480.

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