Upstream fixes from this work

Problems found while building this and reported upstream during the hackathon period. Two of them are silent wrong gradients in Tesseract’s own AD path. Both Tesseract fixes and both Mosaic harness fixes are merged; of the three issues, two are closed and the juliacall deadlock remains open.

Where	What
core#666 / PR 667	The experimental VJP cache compared keys by hash alone with no stored key, so a collision silently served another input’s backward pass. Reproduced on the shipped vectoradd_jax example using hash(-1) == hash(-2), where both are valid norm orders. A second bug in the same path broke apply for non-JAX inputs.
jax#235 / PR 236	jax.jvp shipped the tangent under the wrong list index when only some elements of a list[Differentiable[...]] input were differentiated, so forward and reverse mode disagreed with no error raised.
jax#234	Jitted callbacks deadlock a Tesseract that embeds an in-process Julia runtime, which is why E2b runs against the container. Filed with a minimal reproducer isolating the trigger to Julia allocation inside an off-main-thread callback.
mosaic#126, #141	Harness fixes: Docker setup diagnostics instead of a raw stderr dump, and anomaly status reporting from min_cosine.