fix(core): handle shell line continuations in command splitting (#3600)

Fixes #3158.

`splitCommands()` previously handled backslash escapes before newline/operator splitting, so a chained command like `cd project && \\<LF>git add ...` produced segments starting with a backslash-newline pair, leaving the extracted command root empty and bypassing per-command permission checks for the chained sub-command.

Treat `\\` followed by LF as a removed line continuation, while keeping `\\` followed by CRLF as a normal command separator (bash escapes only \r; the trailing \n still ends the command). This preserves the contract that every chained sub-command is visible to permission parsing and prevents an attacker from hiding a command behind a pseudo-continuation like `echo SAFE \\<CR><LF>rm -rf /`.

Adds regression coverage for both the LF-continuation positive case and the escaped-CRLF safety case.

packages/core/src/utils/shell-utils.test.ts

@@ -442,6 +442,18 @@ describe('getCommandRoots', () => {
     expect(result).toEqual(['grep']);
   });
 
+  it('should treat escaped newlines in chained commands as line continuations', async () => {
+    const result = getCommandRoots(
+      'cd project && \\\ngit add file.php && \\\ngit commit -m "feat"',
+    );
+    expect(result).toEqual(['cd', 'git', 'git']);
+  });
+
+  it('should not treat escaped CRLF as a line continuation', async () => {
+    const result = getCommandRoots('echo SAFE \\\r\nrm -rf /');
+    expect(result).toEqual(['echo', 'rm']);
+  });
+
   it('should filter out empty segments from consecutive newlines', async () => {
     const result = getCommandRoots('ls\n\ngrep foo');
     expect(result).toEqual(['ls', 'grep']);

packages/core/src/utils/shell-utils.ts

@@ -224,6 +224,11 @@ export function splitCommands(command: string): string[] {
     const char = command[i];
     const nextChar = command[i + 1];
 
+    if (!inSingleQuotes && char === '\\' && nextChar === '\n') {
+      i += 2;
+      continue;
+    }
+
     if (char === '\\' && i < command.length - 1) {
       currentCommand += char + command[i + 1];
       i += 2;