feat(lsp+tool-edit-file): multi-server diagnostics + per-edit auto-append

LSP extension:
- Multi-server aggregation: query ALL connected servers matching the
  file's extension (not just the first), merge diagnostics tagged by source
- Incremental sync: capture each server's textDocumentSync.change during
  initialize; compute prefix/suffix diff ranges for change:2 servers;
  full content for change:1 (generic, works for any LSP)
- New diff.ts: pure computeChangeRange + offsetToPosition (O(n), tested)
- Buffer sync: change(filePath, newText) sends didChange with post-edit
  in-memory content; openWithText for first open; tracks open doc text
- languageId mapping: extended with .rb/.rbs/.c/.cpp/etc. (was 'unknown')
- waitForDiagnostics: accepts text override + timeoutMs; returns
  { formatted, slow, timedOut }; polls for publishDiagnostics push
- DiagnosticsStore: hasReceivedPush/clearReceived tracking; formatFiltered
  with minSeverity (1=Error, 2=Warning) for edit_file integration
- LspService.getDiagnostics: service method for cross-extension use

tool-edit-file:
- After successful edit, calls LSP getDiagnostics with post-edit buffer
- Only appends diagnostics with severity ≤ 2 (errors+warnings, no noise)
- Appends slow warning (>10s): 'LSP is taking unusually long...'
- 60s timeout; graceful degradation when no LSP available
- Optional dep on @dispatch/lsp (getService pattern, not manifest depOn)

1468 vitest pass (was 1453, +15 new diff tests).

1 files changed, 18 insertions, 2 deletions

diff --git a/packages/tool-edit-file/src/extension.ts b/packages/tool-edit-file/src/extension.ts
index a4bb19e..bbd8256 100644
--- a/packages/tool-edit-file/src/extension.ts
+++ b/packages/tool-edit-file/src/extension.ts
@@ -1,5 +1,6 @@
 import type { Extension } from "@dispatch/kernel";
-import { createEditFileTool } from "./edit-file.js";
+import { lspServiceHandle } from "@dispatch/lsp";
+import { createEditFileTool, type DiagnosticsHook } from "./edit-file.js";
 
 export const extension: Extension = {
 	manifest: {
@@ -13,6 +14,21 @@ export const extension: Extension = {
 		contributes: { tools: ["edit_file"] },
 	},
 	activate(host) {
-		host.defineTool(createEditFileTool(process.cwd()));
+		// Optional LSP integration: if the lsp extension is loaded, wire its
+		// getDiagnostics service as the post-edit diagnostics hook. If absent,
+		// edits proceed without diagnostics (graceful degradation).
+		const lspService = host.getService(lspServiceHandle);
+		const diagnostics: DiagnosticsHook | undefined = lspService
+			? async (opts) =>
+					lspService.getDiagnostics({
+						filePath: opts.filePath,
+						text: opts.text,
+						cwd: opts.cwd,
+						timeoutMs: 60_000,
+						minSeverity: 2, // errors + warnings only
+					})
+			: undefined;
+
+		host.defineTool(createEditFileTool(process.cwd(), diagnostics));
 	},
 };