Improve detection precision of detect_unfused_reshapes by implementing physical layout verification and first-party attribution filtering:

[copybara-service]

Improve detection precision of detect_unfused_reshapes by implementing physical layout verification and first-party attribution filtering:

1. Physical Relayout Gate (_is_real_relayout): Drop zero-cost logical bitcast reshapes/transposes that preserve physical linearized memory ordering under identical minor-to-major layouts.
2. FLOPs == 0 filter: Exclude misclassified compute operations reporting non-zero FLOPs.
3. Tightened Compute Opcodes: Restrict downstream fold targets to genuinely foldable compute (dot, convolution, einsum, non-collective custom-call).
4. Collective Custom-Call Filter: Exclude collective communications (all-gather, all-to-all, reduce-scatter) which require collective schedule optimization rather than GEMM folding.
5. Fusion-Body Peek: Look inside consumer fusion bodies to verify presence of compute ops (dot/conv) while rejecting pure elementwise fusions.
6. First-Party Attribution Walk: Resolve leaf framework wrapper attributions (flax, jax, etc.) via HLO stack frames to true user model code, dropping orphaned framework wrappers.
7. Source Line Verification: Check source code on disk when available to filter passthrough statements.
8. Deduplication and Ranking: Group duplicate operations by source callsite and result shape, sorting findings by total self-time descending with bytes accessed reported alongside.