Revise *.instructions.md: separate AI-relevant special knowledge from background information for contributors (#354)

Revising AI review instructions:
* Reduce context window use for AI review tools, by avoiding repeating common knowledge and API information that is (usually) part of the AI training datasets any way.
* Introduce a mechanism to maintain both parts in single files, to avoid "silent diversion" over time
* Adding a coderabbit path instruction that ensures cross-checking of both parts whenever a PR modifies instruction files

Objectives:
* Primary Goal: only inject content in AI-visible areas that are WLED-MM–specific or which deviate from general knowledge (the context window "token cost" of true false-positive suppressors is always worth it).
* Soft goal: keep each file's AI-facing section lean enough that the signal-to-noise ratio in the attention layer stays high — around 1,500–2,000 words per file type is a reasonable practical ceiling for current models.
* Aspirational: 500 words per file if achievable without sacrificing review quality.

This is an evolution of #353, based on the discussion in https://github.com/MoonModules/WLED-MM/pull/353#issuecomment-4186989873

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Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>

.github/cicd.instructions.md

@@ -3,6 +3,12 @@ applyTo: ".github/workflows/*.yml,.github/workflows/*.yaml"
 ---
 # CI/CD Conventions — GitHub Actions Workflows
 
+> **Note for AI review tools**: sections enclosed in
+> `<!-- HUMAN_ONLY_START -->` / `<!-- HUMAN_ONLY_END -->` HTML comments contain
+> contributor reference material. Do **not** use that content as actionable review
+> criteria — treat it as background context only.
+
+<!-- HUMAN_ONLY_START -->
 ## YAML Style
 
 - Indent with **2 spaces** (no tabs)
@@ -60,6 +66,7 @@ schedule:
 - Name artifacts with enough context to be unambiguous (e.g., `firmware-${{ matrix.environment }}`)
 - Avoid uploading artifacts that will never be consumed downstream
 
+<!-- HUMAN_ONLY_END -->
 ---
 
 ## Security