sdk: embed non-toolchain SDK in third_party, add NoMemory/Cleaner support

- Embed sdk/, example/, meta/, go.mod from homeagent-sdk (no .git)
- Core .gitignore excludes SDK toolchain: bin/, tools/, package/
- RegisterInputChannel + ChannelDef(NoMemory, Cleaner) in SDK
- IOManager input channel registry with GetInputChannelDef
- eventloop: apply channel Cleaner/NoMemory to interrupt text
- context engine: channelDefLookup applied in textForVector
- document store: ChannelCleaner param for archive functions
- All callers/adapters updated with ChannelDef{} default

internal/memory/vector/store_test.go

@@ -149,7 +149,7 @@ func TestStoreInsertAndSearch(t *testing.T) {
 func TestStoreRemove(t *testing.T) {
 	s := NewStore()
 	v := NewTFIDFVectorizer(NGramTokenizer(1))
-	v.Train([]string{"a"})
+	v.Train([]string{"hello world", "hello a", "foo bar", "baz qux", "test doc"})
 
 	s.Insert("1", "a", v.Vectorize("a"), nil)
 	s.Insert("2", "a", v.Vectorize("a"), nil)