[LJimmy007]

Type of Changes

	Type
✓	🐛 Bug fix

Description

A transform returning None currently stops the remaining transforms because
None.__class__ differs from the node's class. Only check for a type change when
the transform returns a replacement. This preserves the current node and lets
later applicable transforms run, while retaining the existing stop behavior for
replacements of a different type.

Add regression tests for None returns, same-type and different-type replacements,
false predicates, and inference cache invalidation, plus a changelog entry.

Closes #809

Validation on Windows / Python 3.13.5:

• The new None-chain regression fails before the fix; all 14 transform tests pass
  afterward. astroid/transforms.py has 100% line and branch coverage (50
  statements, 20 branches), including every changed line and branch.
• The issue's two-plugin example with Pylint 4.1.3 now calls the second plugin for
  both One and Two.
• Full suite: 2496 passed, 64 skipped, 15 xfailed; five Windows symlink-related
  failures also occur on the unchanged production baseline. No new failures.
• All configured pre-commit checks passed. Prettier 3.9.10 was run separately
  with the configured options using the installed Node runtime.

AI assistance: OpenAI Codex was used for implementation and validation, including
a separate AI review of the diff, regression tests and verification evidence.