Fix crash when completing after import preceded by JSDoc

[Copilot]

Language service panics when requesting completions after an import keyword preceded by JSDoc comments:

/** hello! */
import /*$*/  // Completions crash here

Root Cause

getSingleLineReplacementSpanForImportCompletionNode uses node.Pos() to check if the import spans multiple lines. When JSDoc precedes the import, node.Pos() includes the comment range, incorrectly indicating a multiline span and triggering the panic path.

Changes

• internal/ls/completions.go: Use scanner.GetTokenPosOfNode(node, sourceFile, false) instead of node.Pos() to exclude JSDoc/trivia when checking line span
• internal/fourslash/tests/manual/completionAfterImportWithJSDoc_test.go: Add regression test

Original prompt

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This section details on the original issue you should resolve

<issue_title>Completions crash after import when statement is preceded by JSDoc</issue_title>
<issue_description>```ts
/** hello! /
import /$*/

Request completions at `/*$*/`

[error] panic handling request textDocument/completion: ImportKeyword was necessarily on one line; ImportSpecifier was necessarily parented in an ImportDeclaration
goroutine 15057 [running]:
runtime/debug.Stack()
/usr/local/go/src/runtime/debug/stack.go:26 +0x5e
github.com/microsoft/typescript-go/internal/lsp.(*Server).recover(0xc000140708, {0x441ae5?, 0xc01457e540?}, 0xc027b0ce40)
/workspaces/typescript-go/internal/lsp/server.go:777 +0x4c
panic({0xbf2f40?, 0x10ebe70?})
/usr/local/go/src/runtime/panic.go:783 +0x132
github.com/microsoft/typescript-go/internal/ls.(*LanguageService).getSingleLineReplacementSpanForImportCompletionNode(0xc026445540, 0xc0233a4420)
/workspaces/typescript-go/internal/ls/completions.go:5131 +0x24e
github.com/microsoft/typescript-go/internal/ls.(*LanguageService).getImportStatementCompletionInfo(0xc026445540, 0xc0233a4420, 0xc02734d600?)
/workspaces/typescript-go/internal/ls/completions.go:5107 +0x36d
github.com/microsoft/typescript-go/internal/ls.(*LanguageService).getCompletionData(0xc026445540, {0x10f6028, 0xc026650bd0}, 0xc0122d6608, 0xc0273f0a88, 0xe, 0xc00d0db400)
/workspaces/typescript-go/internal/ls/completions.go:528 +0x30a
github.com/microsoft/typescript-go/internal/ls.(*LanguageService).getCompletionsAtPosition(0xc026445540, {0x10f6028, 0xc026650bd0}, 0xc0273f0a88, 0xe, 0x0)
/workspaces/typescript-go/internal/ls/completions.go:347 +0x35f
github.com/microsoft/typescript-go/internal/ls.(*LanguageService).ProvideCompletion(0xc026445540, {0x10f6028, 0xc026650b10}, {0xc00184c2d0?, 0xc026650b10?}, {0x184c2d0?, 0xc0?}, 0xc027b0ab00)
/workspaces/typescript-go/internal/ls/completions.go:47 +0x11c
github.com/microsoft/typescript-go/internal/lsp.(*Server).handleCompletion(0x418834?, {0x10f6028?, 0xc026650b10?}, 0xc00184c2d0?, 0x10f6028?)
/workspaces/typescript-go/internal/lsp/server.go:1095 +0x39
github.com/microsoft/typescript-go/internal/lsp.init.func1.registerLanguageServiceWithAutoImportsRequestHandler[...].28({0x10f6028, 0xc026650b10}, 0xc027b0ce40)
/workspaces/typescript-go/internal/lsp/server.go:682 +0x16c
github.com/microsoft/typescript-go/internal/lsp.(*Server).handleRequestOrNotification(0xc000140708, {0x10f6060?, 0xc026035ea0?}, 0xc027b0ce40)
/workspaces/typescript-go/internal/lsp/server.go:531 +0x1c6
github.com/microsoft/typescript-go/internal/lsp.(*Server).dispatchLoop.func1()
/workspaces/typescript-go/internal/lsp/server.go:414 +0x3a
created by github.com/microsoft/typescript-go/internal/lsp.(*Server).dispatchLoop in goroutine 10
/workspaces/typescript-go/internal/lsp/server.go:438 +0x9f1

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes Completions crash after import when statement is preceded by JSDoc #2590

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