feat(sources)!: split source contracts into PollSource/StreamSource and add mode-aware source config

- Introduce explicit source interfaces: sources.PollSource and sources.StreamSource, with shared sources.Input (Name() only).
- Remove mandatory Kind() from the base source contract to support sources that emit multiple kinds.
- Add config.SourceMode (poll, stream, or omitted/auto) and SourceConfig.Kinds (plural expected kinds), while keeping legacy SourceConfig.Kind for compatibility.
- Enforce mode semantics in config validation (poll requires every, stream forbids every) and detect mode/driver mismatches in sources.Registry.
- Update docs and tests for the new source model and config behavior.

sources/registry_test.go

@@ -0,0 +1,84 @@
+package sources
+
+import (
+	"context"
+	"strings"
+	"testing"
+
+	"gitea.maximumdirect.net/ejr/feedkit/config"
+	"gitea.maximumdirect.net/ejr/feedkit/event"
+)
+
+type testPollSource struct{ name string }
+
+func (s testPollSource) Name() string { return s.name }
+func (s testPollSource) Poll(context.Context) ([]event.Event, error) {
+	return nil, nil
+}
+
+type testStreamSource struct{ name string }
+
+func (s testStreamSource) Name() string { return s.name }
+func (s testStreamSource) Run(context.Context, chan<- event.Event) error {
+	return nil
+}
+
+func TestRegistryBuildInputModeConflicts(t *testing.T) {
+	r := NewRegistry()
+	r.RegisterPoll("poll_driver", func(cfg config.SourceConfig) (PollSource, error) {
+		return testPollSource{name: cfg.Name}, nil
+	})
+	r.RegisterStream("stream_driver", func(cfg config.SourceConfig) (StreamSource, error) {
+		return testStreamSource{name: cfg.Name}, nil
+	})
+
+	_, err := r.BuildInput(config.SourceConfig{
+		Name:   "s1",
+		Driver: "stream_driver",
+		Mode:   config.SourceModePoll,
+	})
+	if err == nil {
+		t.Fatalf("expected mode conflict error, got nil")
+	}
+	if !strings.Contains(err.Error(), "mode=poll") {
+		t.Fatalf("expected poll conflict error, got: %v", err)
+	}
+
+	_, err = r.BuildInput(config.SourceConfig{
+		Name:   "s2",
+		Driver: "poll_driver",
+		Mode:   config.SourceModeStream,
+	})
+	if err == nil {
+		t.Fatalf("expected mode conflict error, got nil")
+	}
+	if !strings.Contains(err.Error(), "mode=stream") {
+		t.Fatalf("expected stream conflict error, got: %v", err)
+	}
+}
+
+func TestRegistryBuildInputAutoByDriverType(t *testing.T) {
+	r := NewRegistry()
+	r.RegisterPoll("poll_driver", func(cfg config.SourceConfig) (PollSource, error) {
+		return testPollSource{name: cfg.Name}, nil
+	})
+	r.RegisterStream("stream_driver", func(cfg config.SourceConfig) (StreamSource, error) {
+		return testStreamSource{name: cfg.Name}, nil
+	})
+
+	src, err := r.BuildInput(config.SourceConfig{Name: "p", Driver: "poll_driver"})
+	if err != nil {
+		t.Fatalf("BuildInput poll auto failed: %v", err)
+	}
+	if _, ok := src.(PollSource); !ok {
+		t.Fatalf("expected PollSource, got %T", src)
+	}
+
+	src, err = r.BuildInput(config.SourceConfig{Name: "s", Driver: "stream_driver"})
+	if err != nil {
+		t.Fatalf("BuildInput stream auto failed: %v", err)
+	}
+	if _, ok := src.(StreamSource); !ok {
+		t.Fatalf("expected StreamSource, got %T", src)
+	}
+}