Adopt the shared rule set by reference and add the strided-specific rules

[shinaoka]

Part of #199 (Phase 3, rules). Blocked by tensor4all/tensor4all-agent-rules#6, which generalizes the repository-neutral rules (INVARIANT markers, unsafe hygiene, uninit acquisition, cache ownership, # Errors gate, doctest policy, test organization, API evolution, typed errors, Debug, file size, complexity budget, threading principles) into the shared rules repository. Per tenferro's meta-rule, this repo must not vendor copies of cross-repository rules.

Once the shared text lands:

• Update REPOSITORY_RULES.md to reference the shared rules explicitly (which files apply here) instead of duplicating them.
• Keep and sharpen the strided-specific rules: suffix vocabulary decision (see the dedicated issue), ExecutionPolicy as the single threading mechanism plus the exported threshold constant, column-major layout contracts, facade policy (thin re-export only; what qualifies for the root namespace), erased/typed API mirroring expectations, HPTT/faer integration constraints.
• Record the audit gap numbers as the adoption baseline (0 INVARIANT markers; SAFETY on 29 of 418 unsafe blocks; # Errors on 9 of 172; 5 runnable doctests; 53 inline test modules; 13 files over 1000 lines) so remediation issues can be checked off against them.

[shinaoka]

2026-08-10 棚卸し

unblocked on 2026-08-10。blocker tensor4all-agent-rules#6 は completed で close され、shared repository/rust/performance/numerical/docs rules が利用可能。今すぐ REPOSITORY_RULES.md を shared rules の参照に整理し、strided 固有 policy だけを残せる。全9 crate 維持を前提に gap counts を再計測し、#217/#219/#221 の baseline を更新する。

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