feat: implement streaming chat, skill routing, and SAFe PI planning tools

- Add /api/chat/stream endpoint with Server-Sent Events (SSE) for real-time message streaming
  * Implement StreamEvent types (thought, tool_call, tool_result, final, error)
  * Add StreamEventCallback mechanism for event propagation
  * Create StreamChatHandler in webui/bot with proper HTTP headers and flushing

- Implement LLM-based skill router for intelligent capability selection
  * Add optional routerLLM client for semantic routing
  * Implement routeSkillsWithLLM() to match user intent to available skills
  * Add matchSkillsByName() for fuzzy skill matching
  * Update buildUnifiedSystemPrompt() to use routed skills

- Add streaming support to ReAct pipeline
  * Implement runUnifiedReActStream() for streaming thought/action/observation
  * Emit StreamEvent at each ReAct step
  * Support callback error handling in streaming mode

- Integrate three new DevOps tools
  * tools/filedoc: Extract document content from file_id via OpenAI
  * tools/giteaticket: Create Gitea issues from PI plan items with SAFe metadata
  * tools/piplan: Publish PI planning blueprints with dependency tracking

- Add SAFe PI Planning skill
  * Implement PM/SA/RTE (iron triangle) workflow
  * Support for Feature, Enabler, and Dependency definition
  * Automatic task decomposition and Gitea integration

- Create frontend integration documentation
  * Complete SSE protocol specification
  * TypeScript fetch + ReadableStream example
  * LLM-ready refactoring template for other projects

- Simplify file handling
  * Remove legacy file context structures and dual-mode processing
  * Consolidate file operations into UploadAndCacheFiles()
  * Remove FilePromptMode configuration and related complexity

- Update configuration
  * Add Router model support (LLM_ROUTER_MODEL)
  * Add Gitea configuration (BaseURL, Token, Owner, Repo)
  * WebSearch and additional tool infrastructure

Tests: All 22 test packages passing, 8/8 webui tests including 3 new stream tests

tools/filedoc/filedoc_test.go

@@ -0,0 +1,74 @@
+package filedoc
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestNameAndDescription(t *testing.T) {
+	tool := New(Config{APIKey: "k", Model: "gpt-4o-mini"}, 5000, nil)
+	if tool.Name() != "extract_file_document" {
+		t.Fatalf("unexpected tool name: %s", tool.Name())
+	}
+	if tool.Description() == "" {
+		t.Fatal("description should not be empty")
+	}
+}
+
+func TestParseInputPlainFileID(t *testing.T) {
+	id, focus, err := parseInput("file_ec_452e96aad38940229058f193f5c5b9c6_12553222")
+	if err != nil {
+		t.Fatalf("parseInput returned error: %v", err)
+	}
+	if id != "file_ec_452e96aad38940229058f193f5c5b9c6_12553222" {
+		t.Fatalf("unexpected id: %s", id)
+	}
+	if focus != "" {
+		t.Fatalf("expected empty focus, got: %q", focus)
+	}
+}
+
+func TestParseInputFileIDSchemeWithFocus(t *testing.T) {
+	input := "fileid://file_ec_12345\n重点关注风险与建议"
+	id, focus, err := parseInput(input)
+	if err != nil {
+		t.Fatalf("parseInput returned error: %v", err)
+	}
+	if id != "file_ec_12345" {
+		t.Fatalf("unexpected id: %s", id)
+	}
+	if focus == "" {
+		t.Fatal("expected non-empty focus")
+	}
+}
+
+func TestParseInputJSON(t *testing.T) {
+	input := `{"file_id":"file_ec_888", "focus":"提取关键结论"}`
+	id, focus, err := parseInput(input)
+	if err != nil {
+		t.Fatalf("parseInput returned error: %v", err)
+	}
+	if id != "file_ec_888" {
+		t.Fatalf("unexpected id: %s", id)
+	}
+	if focus != "提取关键结论" {
+		t.Fatalf("unexpected focus: %s", focus)
+	}
+}
+
+func TestParseInputInvalid(t *testing.T) {
+	_, _, err := parseInput("hello world")
+	if err == nil {
+		t.Fatal("expected parse error")
+	}
+}
+
+func TestBuildExtractionPrompt(t *testing.T) {
+	p := buildExtractionPrompt("file_ec_abc", "关注测试条目")
+	if p == "" {
+		t.Fatal("prompt should not be empty")
+	}
+	if p != "" && !(strings.Contains(p, "file_ec_abc") && strings.Contains(p, "关注测试条目")) {
+		t.Fatalf("unexpected prompt content: %s", p)
+	}
+}