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, 8 insertions, 8 deletions

diff --git a/internal/lsp/completion_messages_test.go b/internal/lsp/completion_messages_test.go
index bc02645..cd42155 100644
--- a/internal/lsp/completion_messages_test.go
+++ b/internal/lsp/completion_messages_test.go
@@ -7,7 +7,7 @@ import (
 func TestBuildCompletionMessages_InlinePromptOverridesSys(t *testing.T) {
 	s := newTestServer()
 	p := CompletionParams{TextDocument: TextDocumentIdentifier{URI: "file:///x"}, Position: Position{Line: 0, Character: 1}}
-	msgs := s.buildCompletionMessages(true, false, "", false, p, "above", "current", "below", "func f")
+	msgs := s.completion.buildCompletionMessages(true, false, "", false, p, "above", "current", "below", "func f")
 	if len(msgs) < 2 {
 		t.Fatalf("expected messages")
 	}
@@ -22,7 +22,7 @@ func TestBuildCompletionMessages_InlinePromptOverridesSys(t *testing.T) {
 func TestBuildCompletionMessages_ExtraContextIncluded(t *testing.T) {
 	s := newTestServer()
 	p := CompletionParams{TextDocument: TextDocumentIdentifier{URI: "file:///x"}, Position: Position{Line: 0, Character: 1}}
-	msgs := s.buildCompletionMessages(false, true, "EXTRA", false, p, "a", "b", "c", "f")
+	msgs := s.completion.buildCompletionMessages(false, true, "EXTRA", false, p, "a", "b", "c", "f")
 	found := false
 	for _, m := range msgs {
 		if m.Role == "user" && contains(m.Content, "Additional context:") {
@@ -40,11 +40,11 @@ func TestPrefixHeuristic_AllVariants(t *testing.T) {
 	s.cfg.ManualInvokeMinPrefix = 2
 	cur := "a"
 	p := CompletionParams{Position: Position{Line: 0, Character: 1}}
-	if s.prefixHeuristicAllows(false, cur, p, true) {
+	if s.completion.prefixHeuristicAllows(false, cur, p, true) {
 		t.Fatalf("should require >=2 prefix on manual invoke")
 	}
 	// structural triggers 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")
 	}
 }
@@ -52,7 +52,7 @@ func TestPrefixHeuristic_AllVariants(t *testing.T) {
 func TestBuildDocString_Contents(t *testing.T) {
 	s := newTestServer()
 	p := CompletionParams{TextDocument: TextDocumentIdentifier{URI: "file:///x"}, Position: Position{Line: 3, Character: 7}}
-	got := s.buildDocString(p, "above", "current", "below", "func ctx")
+	got := s.completion.buildDocString(p, "above", "current", "below", "func ctx")
 	if !contains(got, "file: file:///x") || !contains(got, "line: 3") || !contains(got, "function: func ctx") {
 		t.Fatalf("unexpected doc string: %q", got)
 	}
@@ -61,7 +61,7 @@ func TestBuildDocString_Contents(t *testing.T) {
 func TestBuildCompletionMessages_InParams_UsesParamPrompts(t *testing.T) {
 	s := newTestServer()
 	p := CompletionParams{TextDocument: TextDocumentIdentifier{URI: "file:///x"}, Position: Position{Line: 0, Character: 5}}
-	msgs := s.buildCompletionMessages(false, false, "", true, p, "a", "func f(x)", "c", "func f(x)")
+	msgs := s.completion.buildCompletionMessages(false, false, "", true, p, "a", "func f(x)", "c", "func f(x)")
 	if len(msgs) < 2 || msgs[0].Role != "system" || msgs[1].Role != "user" {
 		t.Fatalf("unexpected messages")
 	}
@@ -73,12 +73,12 @@ func TestBuildCompletionMessages_InParams_UsesParamPrompts(t *testing.T) {
 func TestPostProcessCompletion_CodeFencesAndDuplicates(t *testing.T) {
 	s := newTestServer()
 	// code fences
-	cleaned := s.postProcessCompletion("```go\nname := value\n```", "", "")
+	cleaned := s.completion.postProcessCompletion("```go\nname := value\n```", "", "")
 	if cleaned == "" {
 		t.Fatalf("expected non-empty after fence removal")
 	}
 	// duplicate assignment prefix strip
-	cleaned2 := s.postProcessCompletion("name := other", "name := ", "name := ")
+	cleaned2 := s.completion.postProcessCompletion("name := other", "name := ", "name := ")
 	if cleaned2 == "" || cleaned2 == "name := other" {
 		t.Fatalf("expected duplicate assignment prefix stripped: %q", cleaned2)
 	}