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/core/agent_tools_test.go

@@ -22,6 +22,7 @@ func (d *mockOutputDevice) Tools() []agentIO.ToolDef              { return d.too
 func (d *mockOutputDevice) Start() error                          { return nil }
 func (d *mockOutputDevice) Stop() error                           { return nil }
 func (d *mockOutputDevice) OutputCapabilities() agentIO.OutputCapability { return d.caps }
+func (d *mockOutputDevice) ChannelDef() agentIO.ChannelDef { return agentIO.ChannelDef{} }
 func (d *mockOutputDevice) Execute(tool string, args map[string]interface{}) (interface{}, error) {
 	if d.toolFn != nil {
 		return d.toolFn(tool, args)