docs: registration is the caller's job — correct stale auto-call claims

The autolens/jax/registration.py module docstring claimed register_tracer_classes
"is called automatically by PointSolver(use_jax=True).solve(tracer, ...) on the
first invocation and by Simulator(use_jax=True).via_tracer_from(tracer, ...) ...
once Phase 2 ships the Simulator changes".

Neither is true. grep finds no caller anywhere in autolens. And it cannot be
done automatically: PointSolver.solve_triangles already carries the reason at its
own call site (point_solver.py:102-109) — JAX flattens a jitted function's
arguments at trace time, before entering the callee, so registration must run
before the first jitted call.

Corrected to state that calling it is the user's responsibility, with the
trace-time reason, and to cross-reference the new autogalaxy counterpart
autogalaxy.jax.register_galaxies_classes (PyAutoGalaxy#537).

Docstring only — no behaviour change, no API surface.

Refs PyAutoLabs/autolens_workspace#379

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CWqjHGXUut25TEB8octU8H

Author: 2 people

autolens/jax/registration.py

@@ -7,10 +7,16 @@
 
 This module is the counterpart of ``AnalysisImaging._register_fit_imaging_pytrees``
 for code paths that do not go through ``Analysis`` (point-source solving,
-custom forward models, hand-built simulators). It is called automatically
-by ``PointSolver(use_jax=True).solve(tracer, ...)`` on the first invocation
-and by ``Simulator(use_jax=True).via_tracer_from(tracer, ...)`` in PyAutoLens
-once Phase 2 ships the Simulator changes.
+custom forward models, hand-built simulators).
+
+**Calling it is the user's responsibility.** Nothing in the library calls it
+for you, and nothing can: JAX flattens a jitted function's arguments at trace
+time, i.e. *before* entering the callee, so a ``solve()`` or
+``via_tracer_from()`` that registered internally would already be too late.
+``PointSolver.solve_triangles`` carries the same note at its own call site.
+Register once, before the first ``@jax.jit`` invocation.
+
+The autogalaxy counterpart is ``autogalaxy.jax.register_galaxies_classes``.
 
 Mirrors PyAutoFit's ``autofit/jax/pytrees.py`` layout. Idempotent: re-registration
 of a class is a silent no-op.