Add README, task format docs, fix archived memos API

- README.md: introduction, features, build/install, tech stack,
  disclaimer, acknowledgements, logo at top
- TASK_FORMAT.md: full task syntax reference with examples,
  validation rules, typo detection, notification behavior
- Fix archived memos: use state query param instead of CEL filter
- LOGO.md: remove triangle variant, keep circle only
- logo-circle.svg tracked for README rendering

Signed-off-by: Avinal Kumar <avinal.xlvii@gmail.com>
Co-Authored-By: Claude Opus 4.6 (1M context)

composeApp/src/commonMain/kotlin/com/avinal/memos/api/MemosApiClient.kt

@@ -141,7 +141,7 @@ class MemosApiClient(
     suspend fun listArchivedMemos(): ApiResult<ListMemosResponse> = apiCall {
         httpClient.get(url("/memos")) {
             parameter("pageSize", 50)
-            parameter("filter", "state == \"ARCHIVED\"")
+            parameter("state", "ARCHIVED")
         }.body()
     }