Refactor lsp.Server God Object: extract chat and completion subsystems

The Server type accumulated two large, tangled feature subsystems (in-editor
chat and code completion) alongside its core LSP dispatch role. Pull them into
cohesive types that own their state and logic while delegating shared
infrastructure back to Server via a back-reference.

- Add completionService (completion_service.go): owns the completion
  cache/throttle state (completionState) and all completion request-handling
  logic (handleCompletion, plan/jobs/execute, provider-native path,
  post-processing, message building, prefix heuristics). Methods moved off
  Server in handlers_completion.go to completionService.
- Add chatService (chat_service.go + chat_handlers.go): owns the input-activity
  clock (lastInput, with its own mutex instead of Server.mu) and all in-editor
  chat logic (detection, transcript history, message building, edit
  application, inline prompts) plus the slash-command handlers
  (chat_commands.go).
- Server now holds chat/completion fields, wires them in NewServer, and
  delegates (dispatch table, didChange, debounce gate) to them. Thin Server
  shims preserve the existing completion-state API for callers/tests.

Pure refactor: no behavior or LSP protocol changes. Tests adjusted only to
reach the relocated methods/state via the services. All tests pass with -race;
coverage 86.1%.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 5 insertions, 5 deletions

diff --git a/internal/lsp/chat_context_mode_test.go b/internal/lsp/chat_context_mode_test.go
index 876f092..e6696f4 100644
--- a/internal/lsp/chat_context_mode_test.go
+++ b/internal/lsp/chat_context_mode_test.go
@@ -23,7 +23,7 @@ func TestChat_RespectsContextModeWindow(t *testing.T) {
 	src := "package main\nline2 context\nwhat?>\n"
 	s.setDocument(uri, src)
 
-	s.detectAndHandleChat(uri)
+	s.chatSvc().detectAndHandleChat(uri)
 	s.inflight.Wait()
 	if len(cap.msgs) == 0 {
 		t.Fatalf("expected Chat to be called")
@@ -59,7 +59,7 @@ func TestChat_ContextModeMinimal_NoExtra(t *testing.T) {
 
 	uri := "file:///ctx2.go"
 	s.setDocument(uri, "package main\nhelp?>\n")
-	s.detectAndHandleChat(uri)
+	s.chatSvc().detectAndHandleChat(uri)
 	s.inflight.Wait()
 
 	if len(cap.msgs) != 2 {
@@ -81,7 +81,7 @@ func TestChat_ContextModeAlwaysFull_AddsExtra(t *testing.T) {
 
 	uri := "file:///ctx3.go"
 	s.setDocument(uri, "package main\nline2\nhelp?>\n")
-	s.detectAndHandleChat(uri)
+	s.chatSvc().detectAndHandleChat(uri)
 	s.inflight.Wait()
 
 	if len(cap.msgs) < 3 {
@@ -109,7 +109,7 @@ func TestChat_ContextModeFileOnNewFunc_NoExtraWithoutSignature(t *testing.T) {
 
 	uri := "file:///ctx4.go"
 	s.setDocument(uri, "package main\nhelp?>\n")
-	s.detectAndHandleChat(uri)
+	s.chatSvc().detectAndHandleChat(uri)
 	s.inflight.Wait()
 
 	if len(cap.msgs) != 2 {
@@ -130,7 +130,7 @@ func TestChat_ContextModeFileOnNewFunc_WithSignature_AddsExtra(t *testing.T) {
 	// Signature without '{' yet; chat prompt appears before the body, so newFunc=true
 	src := "package main\n\nfunc add(x int) int\nhelp?>\n"
 	s.setDocument(uri, src)
-	s.detectAndHandleChat(uri)
+	s.chatSvc().detectAndHandleChat(uri)
 	s.inflight.Wait()
 
 	if len(cap.msgs) < 3 {