Remove multine error message from stack correctly

[cderv]

❯ quarto convert "line 1

line 2

line 3

line 4"
ERROR: File not found: 'line 1

line 2

line 3

line 4'

Stack trace:
    at Command.actionHandler (file:///home/cderv/project/quarto-cli/src/command/convert/cmd.ts:54:13)
    at async Command.execute (https://deno.land/x/[email protected]/command/command.ts:1948:7)
    at async Command.parseCommand (https://deno.land/x/[email protected]/command/command.ts:1780:14)
    at async quarto (file:///home/cderv/project/quarto-cli/src/quarto.ts:190:5)
    at async file:///home/cderv/project/quarto-cli/src/quarto.ts:219:5
    at async file:///home/cderv/project/quarto-cli/src/core/main.ts:41:14
    at async mainRunner (file:///home/cderv/project/quarto-cli/src/core/main.ts:43:5)
    at async file:///home/cderv/project/quarto-cli/src/quarto.ts:209:3

I get this now on Linux

Previously it was

❯ quarto convert "line 1

line 2

line 3

line 4"
ERROR: File not found: 'line 1

line 2

line 3

line 4'

Stack trace:

line 2

line 3

line 4'
    at Command.actionHandler (file:///home/cderv/.local/share/qvm/versions/v1.6.42/bin/quarto.js:108237:15)
    at async Command.execute (file:///home/cderv/.local/share/qvm/versions/v1.6.42/bin/quarto.js:8111:13)
    at async Command.parseCommand (file:///home/cderv/.local/share/qvm/versions/v1.6.42/bin/quarto.js:8001:20)
    at async quarto (file:///home/cderv/.local/share/qvm/versions/v1.6.42/bin/quarto.js:126627:9)
    at async file:///home/cderv/.local/share/qvm/versions/v1.6.42/bin/quarto.js:126654:9
    at async mainRunner (file:///home/cderv/.local/share/qvm/versions/v1.6.42/bin/quarto.js:126519:9)
    at async file:///home/cderv/.local/share/qvm/versions/v1.6.42/bin/quarto.js:126645:5
````

(on Windows multiline input is not easy to add so I don't get the same error)

@cscheid do you think this is valid to remove anything in stack before first `  at` line ? 

[cscheid]

Yes, this is a good "fix". It's never going to work perfectly. For example, I think this now breaks if a file name matches /^\s*at /. But it's a good enough improvement.

It would be really great if Deno gave JSON-readable stacks.

[cderv]

Ok great! thank you !