Improve types in assignment_collection

[alexfikl]

This essentially adds types to SymbolicAssignmentCollection and fixes some things around it as well.

It also adds some basic types to sumpy.cse, mainly to functions that are called from the outside. Not very sure about these, since I don't understand the algorithms / data structures used in there, but pyright seems to not complain too much..

[Copilot]

Pull request overview

This PR focuses on tightening type annotations around SymbolicAssignmentCollection and exposing more explicit types in sumpy.cse, along with a few small type-related touchups across the codebase and an updated basedpyright baseline.

Changes:

• Add/adjust type annotations for SymbolicAssignmentCollection and related helper classes.
• Add type annotations to sumpy.cse public functions and internal helpers.
• Update a few signatures/overrides in supporting modules and refresh the basedpyright baseline.

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
sumpy/version.py	Fix _parse_version to use its version parameter.
sumpy/tools.py	Type-annotate OrderedSet and add override usage.
sumpy/cse.py	Add type annotations and refactor imports/types around CSE.
sumpy/codegen.py	Widen assignment expression type from sym.Expr to sym.Basic.
sumpy/assignment_collection.py	Add types/docs to SymbolicAssignmentCollection and its symbol generator.
sumpy/array_context.py	Add type annotations for make_loopy_program and pytest factory overrides.
.basedpyright/baseline.json	Update baseline to reflect new typing work.

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[alexfikl]

@inducer The remaining pyright failures here seem to be because inducer/pytools#350 is not released yet. Would you prefer I update the baseline without that or wait for a release?

[inducer]

https://github.com/inducer/pytools/releases/tag/v2026.1