Description of problem:

When running `tkn pac cel` Without any arguments or with only headers/body, the command fails with misleading error messages. Instead of clearly informing that both -b (body) and -H (headers) are required, it displays low-level messages such as 'auto-detection failed', 'unexpected end of JSON input', or 'unknown X-Gitlab-Event'. This makes it hard to understand what is actually missing from the command.

Prerequisites (if any, like setup, operators/versions):

tkn-pac 0.39.2

Steps to Reproduce

Install the latest Tkn PAC CLI (0.39.2)

pac tkn pac cel

pac tkn pac cel -H gitlab-headers.txt

pac tkn pac cel -b gitlab-payload.json

Actual results:

➜  pac tkn pac cel
Error: auto-detection failed: unable to detect provider from headers or payload

➜  pac tkn pac cel -H gitlab-headers.txt
Error: unexpected end of JSON input

➜  pac tkn pac cel -b gitlab-payload.json
Error: unknown X-Gitlab-Event 

Expected results:

Error: body (-b) and headers (-H) are required to evaluate CEL expressions