Build History for pull/450

fix: preserve batch/input axes in output-axis block tensor concat spec The output-axis concat spec "bt0,...; bt1,..." dropped batch and input rows, causing shape errors when list block tensor components had input or batch axes. Use the full spec "...|...-> bt0,...; ..." to broadcast batch/input rows through concatenation. Add test 13 exercising list block tensors with input-dim components. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

test: add block tensor regression tests and fix stale doc wording Add ndarray constant regressions (tuple, list, array) to pin the first-leaf disambiguation heuristic, and a tuple-in-apply test to lock Pexp_apply tuple preservation. Remove "upcoming"/"planned" wording from syntax_extensions.md, migration_guide.md, and slides-shapes_and_einsum.md. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

fix: support nested block tensor literals [[ta; tb]; [tc; td]] Add Concat-Concat element-wise unification case to row.ml's unify_dim, allowing the shape solver to equate structurally-matching Concat dimensions from inner block tensor results when used in outer block tensors. Update test and docs to demonstrate direct nesting (2x2 block matrix). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

fix: support nested block tensor literals [[ta; tb]; [tc; td]] Add Concat-Concat element-wise unification case to row.ml's unify_dim, allowing the shape solver to equate structurally-matching Concat dimensions from inner block tensor results when used in outer block tensors. Update test and docs to demonstrate direct nesting (2x2 block matrix). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

fix: support nested block tensor literals [[ta; tb]; [tc; td]] Add Concat-Concat element-wise unification case to row.ml's unify_dim, allowing the shape solver to equate structurally-matching Concat dimensions from inner block tensor results when used in outer block tensors. Update test and docs to demonstrate direct nesting (2x2 block matrix). Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>