Standardize error handling with specific exit codes

[ayushman1210]

Description:
Error handling uses inconsistent patterns:

• Some functions use exit(1) (generic)
• Some use exit(EXIT_CODE_*) (specific error codes)
• Some log errors before exiting, some don't

Location: At various places in the codebase

Example from modelParams.c:

if (!okay) {
  exit(1);  // Line 69 - generic exit code
}

// vs.

logError("format unrecognized in climate file...\n");
exit(EXIT_CODE_INPUT_FILE_ERROR);  // Line 184 - specific code with message

Changes

Standardize on using specific exit codes with error messages:

if (!okay) {
  logError("Required parameters missing from parameter file\n");
  exit(EXIT_CODE_INPUT_FILE_ERROR);
}

[ayushman1210]

Hi @dlebauer
just checking in to see if you’ve had a chance to look at this PR when you get a moment.
Happy to make any changes or answer questions.
Thanks!!

[Alomir]

Looks good, thanks for cleaning up the code! (One minor suggestion to change)

[ayushman1210]

Hi @Alomir ,
I noticed that the GitHub Actions workflow for my PR is failing due to the Lychee link checker. The error is caused by the http://contributor-covenant.org link in CODE_OF_CONDUCT.md being temporarily unreachable, not by any code changes.
I can either update the link to use HTTPS or add a Lychee exclusion for it so the workflow passes.
Would you like me to make that fix, or should we ignore the Lychee check for this PR?

[Alomir]

Also, the sipnet.out files should not be deleted

[Alomir]

I prefer the change to .gitignore in #253; please remove that file from this PR, and you'll be good to go!