[Michael Duggan (miduggan24)]

Summary

As part of linked ticket, common file is implemented in docs space for CRTP documentation to avoid duplication across apps
https://github.com/SiliconLabsSoftware/docs-matter/pull/68/changes

This doc however is not suitable for matter_sdk as some references (in particular links to file locations) are not accurate for this repo.

Implement common doc in docs/platforms/silabs/silabs_extending_base_app_implementation.md and link to this from all app README files.

Keep EVSE and closure specific documentation (for energy management and ClosureManager respectively)

Related issues

MATTER-5943

Testing

n/a docs only

[cursor]

PR Summary

Low Risk
Documentation-only refactor with no runtime or build changes.

Overview
Adds a single Silicon Labs platform guide at docs/platforms/silabs/silabs_extending_base_app_implementation.md for customizing sample apps via CustomerAppTask and CRTP *Impl() hooks (override workflow, data model callback routing post–Matter Extension 2.9.0, lighting-style sample code, and StartAppTask notes). The guide uses matter_sdk–accurate paths to examples/platform/silabs/customer/ and related sources.

Registers the page on docs/platforms/silabs/index.md and replaces large duplicated “Extending Base App Implementation” blocks in many Silabs example READMEs with a short link to the shared doc plus pointers to each app’s include/AppTaskImpl.h and src/AppTask.cpp.

Closure and EVSE READMEs still carry app-specific material: closure keeps CustomerAppManager / ClosureManager CRTP docs; EVSE keeps Energy Management Hardware Integration (delegates not yet on CRTP).

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