[Michael Duggan (miduggan24)]

Issue Link:
n/a

Description of Problem/Feature:
need common documentation changes on release_2.10 branch

Description of Fix/Solution:
cherry-pick #931 and #1146 to implement common documentation changes for project upgrades

Testing Done:
n/a doc only

[cursor]

PR Summary

Low Risk
Documentation-only edits with no runtime or build impact; readers now depend on external docs.silabs.com URLs staying valid for 2.10.0.

Overview
Deduplicates the long, copy-pasted Extending Base App Implementation sections across Matter example READMEs (Thread/Wi‑Fi variants) by replacing them with a short pointer to the Matter 2.10.0 API reference and local autogen/AppTaskImpl.h / autogen/AppTask.cpp hooks.

Closure examples keep app-specific CustomerAppManager / ClosureManager guidance but drop repeated CustomerAppTask prose and sample code; they link to the shared doc for AppTask behavior, expand the table of contents, and narrow the override API table to ClosureManager autogen files only.

EVSE READMEs get the same AppTask shortcut plus a TOC entry for Energy Management Hardware Integration (unchanged body). Fan and thermostat Wi‑Fi alternate READMEs gain the new short extending section and TOC link where it was missing.

^{Reviewed by Cursor Bugbot for commit fa3f6c0. Configure here.}