reactor(cli): move memoh cli to tui

1. Split the oversized `cmd/agent` entrypoint into a multi-file package and update dev/build scripts to use the package path instead of compiling `main.go` directly.
2. Add a new `memoh` terminal UI for local bot chat, with Bubble Tea

docker/Dockerfile.server

@@ -33,7 +33,7 @@ RUN --mount=type=cache,target=/go/pkg/mod \
       -X github.com/memohai/memoh/internal/version.Version=${VERSION} \
       -X github.com/memohai/memoh/internal/version.CommitHash=${COMMIT_HASH} \
       -X github.com/memohai/memoh/internal/version.BuildTime=${BUILD_TIME}" \
-    -o memoh-server ./cmd/agent/main.go
+    -o memoh-server ./cmd/agent
 
 # ---- Stage 3: Build bridge binary ----
 FROM build-base AS bridge-builder