REDI-101: remove AI/tooling attribution from docs & source comments

Make the repo read as a hand-authored reference project by dropping
references to the authoring tooling — the internal convention "skills", the
Linear backlog, and the REDI issue ids — from the README and source comments.

- README: remove the "Convention skills index" section and its TOC entry,
  strip every `See **android-...**` / koin-constructor-dsl citation, drop the
  Linear backlog link, and reword the REDI-99 Room reference to "an optional
  stretch".
- Source comments: neutralize the four skill citations in HttpClientExt,
  CharactersPresentationModule, CharacterListRobot, ErrorDemoViewModel.
- Also correct the testing section that the MockK migration left stale: it
  described "Fakes, not mocks" / FakeCharacterRepository (now deleted) — now
  describes MockK, and adds MockK to the stack lists.

Verified: git grep finds no AI/Claude/Anthropic/Linear/skill references in any
tracked file; assembleDebug + assembleDebugAndroidTest green.

core/data/src/main/kotlin/com/example/architecture/core/data/network/HttpClientExt.kt

@@ -98,7 +98,7 @@ internal fun logNetworkError(throwable: Throwable, message: String) {
     Timber.tag("HttpClient").e(throwable, message)
 }
 
-/** Maps HTTP status codes to typed [DataError.Network] (extends the skill table with 400/403/404). */
+/** Maps HTTP status codes to typed [DataError.Network] (covering 400/403/404 as well). */
 suspend inline fun <reified T> responseToResult(
     response: HttpResponse,
 ): Result<T, DataError.Network> {