Merge pull request #4824 from Repiteo/type-hints-environment

Implement type hints for Environment and environment utilities

Author: bdbaddog

CHANGES.txt

@@ -26,6 +26,7 @@ RELEASE  VERSION/DATE TO BE FILLED IN LATER
     - Purge vim/emac local variable bloat.
     - Implement type hints for Node subclasses.
     - Ruff: Handle F401 exclusions more granularly, remove per-file exclusions.
+    - Implement type hints for Environment and environment utilities.
     - Deprecated Python 3.7 & 3.8 support.
 
   From William Deegan:

RELEASE.txt

@@ -105,6 +105,7 @@ DEVELOPMENT
 - Unify internal "_null" sentinel usage.
 - Docbook tests: improve skip message, more clearly indicate which test
   need actual installed system programs (add -live suffix).
+- Implement type hints for Environment and environment utilities.
 
 - MSVC: Added a host/target batch file configuration table for Visual
   Studio 2026.  Visual Studio 2026 removed support for 32-bit arm targets.