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, 2 insertions, 1 deletions

diff --git a/bun.lock b/bun.lock
index 816651a..44e7bcd 100644
--- a/bun.lock
+++ b/bun.lock
@@ -220,6 +220,7 @@
       "version": "0.0.0",
       "dependencies": {
         "@dispatch/kernel": "workspace:*",
+        "@dispatch/lsp": "workspace:*",
       },
     },
     "packages/tool-read-file": {
@@ -270,7 +271,7 @@
     },
     "packages/transport-contract": {
       "name": "@dispatch/transport-contract",
-      "version": "0.18.0",
+      "version": "0.21.0",
       "dependencies": {
         "@dispatch/ui-contract": "workspace:*",
         "@dispatch/wire": "workspace:*",