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/agent/io/channel_test.go

@@ -43,6 +43,7 @@ func (d *mockDevice) Stop() error {
 	return nil
 }
 func (d *mockDevice) OutputCapabilities() OutputCapability { return d.caps }
+func (d *mockDevice) ChannelDef() ChannelDef { return ChannelDef{} }
 func (d *mockDevice) Execute(tool string, args map[string]interface{}) (interface{}, error) {
 	if d.executeFn != nil {
 		return d.executeFn(tool, args)