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, 2 insertions, 2 deletions

diff --git a/internal/lsp/chat_trigger_suppression_test.go b/internal/lsp/chat_trigger_suppression_test.go
index 852f955..8cfd178 100644
--- a/internal/lsp/chat_trigger_suppression_test.go
+++ b/internal/lsp/chat_trigger_suppression_test.go
@@ -7,13 +7,13 @@ func TestCompletionSuppressedOnChatTriggerEOL(t *testing.T) {
 	s := newTestServer()
 	s.cfg.MaxTokens = 32
 	s.cfg.TriggerCharacters = []string{".", ":", "/", "_"}
-	s.compCache = make(map[string]string)
+	s.completion.compCache = make(map[string]string)
 	initServerDefaults(s)
 	s.llmClient = &countingLLM{}
 	tests := []string{"What now?>", "Explain!>", "Refactor:>", "note ;>"}
 	for i, line := range tests {
 		p := CompletionParams{Position: Position{Line: 0, Character: len(line)}, TextDocument: TextDocumentIdentifier{URI: "file://chat-suppr.go"}}
-		items, ok, _ := s.tryLLMCompletion(p, "", line, "", "", "", false, "")
+		items, ok, _ := s.completion.tryLLMCompletion(p, "", line, "", "", "", false, "")
 		if !ok {
 			t.Fatalf("case %d: expected ok=true", i)
 		}