docs: cli_reference.md documents --no-scan flag that doesn't exist in vajax/cli.py

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Problem

docs/cli_reference.md line 52 includes --no-scan in the run command options table:

| `--no-scan` | Disable lax.scan (use Python loop) |

However, this flag does not exist in vajax/cli.py. The actual CLI arguments defined there are: --sparse, --gpu, --cpu, --x64, --x32, --profile, --tran, --ac, -o/--output, -f/--format. There is no --no-scan argument.

Steps to verify

vajax run --help  # --no-scan does not appear
grep 'no.scan' vajax/cli.py  # no results

Fix

Remove the --no-scan row from the options table in docs/cli_reference.md, or implement the flag if it was intended.