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/completion_helpers_more_test.go b/internal/lsp/completion_helpers_more_test.go
index 79d2523..9e4cdac 100644
--- a/internal/lsp/completion_helpers_more_test.go
+++ b/internal/lsp/completion_helpers_more_test.go
@@ -26,10 +26,10 @@ func TestShouldSuppressForChatTriggerEOL(t *testing.T) {
 	s := newTestServer()
 	p := CompletionParams{TextDocument: TextDocumentIdentifier{URI: "file:///x"}, Position: Position{Line: 0, Character: 10}}
 	line := "say hi;>"
-	if !s.shouldSuppressForChatTriggerEOL(line, p) {
+	if !s.completion.shouldSuppressForChatTriggerEOL(line, p) {
 		t.Fatalf("expected suppression when ;> at EOL")
 	}
-	if s.shouldSuppressForChatTriggerEOL("plain>", p) {
+	if s.completion.shouldSuppressForChatTriggerEOL("plain>", p) {
 		t.Fatalf("should not suppress for plain >")
 	}
 }
@@ -37,15 +37,15 @@ func TestShouldSuppressForChatTriggerEOL(t *testing.T) {
 func TestPrefixHeuristicAllows(t *testing.T) {
 	s := newTestServer()
 	// inline prompt allows zero prefix
-	if !s.prefixHeuristicAllows(true, "", CompletionParams{Position: Position{Line: 0, Character: 0}}, false) {
+	if !s.completion.prefixHeuristicAllows(true, "", CompletionParams{Position: Position{Line: 0, Character: 0}}, false) {
 		t.Fatalf("inline prompt should allow")
 	}
 	// structural triggers like '.' allow without prefix
-	if !s.prefixHeuristicAllows(false, "fmt.", CompletionParams{Position: Position{Line: 0, Character: 4}}, false) {
+	if !s.completion.prefixHeuristicAllows(false, "fmt.", CompletionParams{Position: Position{Line: 0, Character: 4}}, false) {
 		t.Fatalf("dot trigger should allow")
 	}
 	// otherwise need at least minimal prefix (default min=1)
-	if s.prefixHeuristicAllows(false, " ", CompletionParams{Position: Position{Line: 0, Character: 0}}, false) {
+	if s.completion.prefixHeuristicAllows(false, " ", CompletionParams{Position: Position{Line: 0, Character: 0}}, false) {
 		t.Fatalf("should not allow with no prefix")
 	}
 }