test(lsp): improve handler test coverage from 22% to 68%

- Add completion_test.go: tests for top-level, ingredient.method,
  property, requisite type, and step ID completions
- Add hover_test.go: tests for markdown generation, word extraction,
  and edge cases
- Add diagnostics_test.go: tests for nil recipe, parse errors, empty
  ingredient, requisite validation, range helpers
- Update all dependencies to latest versions
- Add target/ to .gitignore (stale Rust build artifacts)

.gitignore

@@ -1,2 +1,3 @@
 grlx-lsp
 dist/
+target/