Test organization: extract inline cfg(test) modules; resolve strided-perm's test-gated implementation modules

[shinaoka]

Scope correction (2026-08-10)

strided-einsum2 and strided-opteinsum are not being retired. Per #226, all nine workspace crates remain maintained. Any retirement/Phase 2 removal premise below is obsolete; re-audit and implement the acceptance criteria across the maintained workspace.

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Part of #199 (Phase 3, organization). All file:line references are pinned to origin/main at 9da9b9f.

53 inline #[cfg(test)] mod blocks live in src/ across the workspace (largest in the retained crates: strided-kernel/src/fused.rs:1498 at 576 lines, block.rs:251 at 469, kernel.rs:660 at 418, strided-view/src/view.rs:1015 at 337, map_view.rs:2289 at 289, simd.rs:910 at 283). Zero crates use the src/<module>/tests/*.rs pattern.

Separately, strided-perm/src/lib.rs:14 gates three whole implementation modules behind #[cfg(test)] (block, kernel with an unexplained #[allow(dead_code)], order): about 1000 lines of dead-in-release code shipped in src/.

• Extract inline test modules to src/<module>/tests/*.rs with #[cfg(test)] mod tests; stubs, per the test-organization rule (across all nine maintained crates).
• Decide the strided-perm trio: fold into test-support files, delete, or document why they ship in src/.
• This also shrinks several files counted against the 1000-line trigger; re-measure afterwards and split what remains oversized along real boundaries (erased.rs at 4067 lines splits naturally by plan family).

[shinaoka]

2026-08-10 棚卸し

active, large mechanical series。inline #[cfg(test)] modules と strided-perm の test-gated implementation modules は current main に残る。一括巨大 diff にせず crate/module ownership ごとの focused PR に分割し、挙動変更なしを test count と workspace tests で確認。最後に oversized files を再計測し、実責務境界だけで split する。

Umbrella: #230。実装 PR の base は umbrella/issue-burndown-2026-08。