Fix red arg to subst

[inducer]

@majosm This became much bigger than I had hoped. I'd like it if you could take a quick look at the changes in reduction_arg_to_subst_rule.

[Copilot]

Pull request overview

This PR refactors reduction_arg_to_subst_rule to use Loopy’s rule-aware mapping machinery (with stack matching via within) so that reduction arguments can be rewritten more robustly, alongside a broader set of typing/documentation cleanups (notably around instruction IDs and barrier/no-sync kinds).

Changes:

• Reworked reduction_arg_to_subst_rule to use a RuleAwareIdentityMapper-based mapper with within stack matching.
• Introduced/propagated stronger typing for instruction IDs (InsnId), barrier kinds (BarrierKind), and no-sync scopes (NoSyncScope) across transforms/scheduling/instruction definitions.
• Updated Sphinx documentation/config to reference the new type aliases.

Reviewed changes

Copilot reviewed 11 out of 12 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
loopy/typing.py	Adds InsnId to the public typing docs.
loopy/transform/data.py	Refactors reduction_arg_to_subst_rule to rule-aware mapping + adds typing.
loopy/transform/add_barrier.py	Tightens typing of barrier kind arguments using BarrierKind.
loopy/symbolic.py	Fixes reduction callback typing to use Reduction instead of Expression.
loopy/schedule/__init__.py	Propagates barrier/no-sync typing and adds more explicit type annotations.
loopy/kernel/instruction.py	Introduces NoSyncScope, BarrierKind, and to_barrier_kind; tightens no_sync_with typing.
loopy/kernel/creation.py	Uses to_barrier_kind when creating barrier instructions from textual syntax.
loopy/kernel/array.py	Narrows ArrayBase.offset type annotation (currently inconsistent with runtime behavior).
loopy/kernel/__init__.py	Tightens typing for no-sync scope queries and adds type annotations.
doc/ref_kernel.rst	Attempts to document new type aliases (currently using autoclass).
doc/conf.py	Adds missing-reference aliases for the new type aliases.

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[inducer]

All better now. This was badly broken previously.