Make shared path optional in ioda-dump

[Copilot]

The shared path configuration was required for all file types but only used for ODB files, forcing users processing NC/HDF5/BUFR files to supply unnecessary configuration.

Changes

• Default value: Set shared path to "./" when not specified, with warning logged
• Dead code removal: Eliminated redundant empty check (always has default now)
• Documentation: Clarified shared path is optional and ODB-specific

Implementation

// Before: exception if not defined
if (fullConfig.has("shared path")) {
   fullConfig.get("shared path", sharedPath);
} else {
   throw eckit::Exception("Missing 'Shared Path' in YAML configuration");
}

// After: default with warning
if (fullConfig.has("shared path")) {
   fullConfig.get("shared path", sharedPath);
} else {
   sharedPath.push_back("./");
   oops::Log::warning() << "Shared Path not defined in YAML configuration, using default: './' " << std::endl;
}

ODB files will fail with clear file-not-found errors if mapping/query files don't exist at the default path.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Shared Path should be optional</issue_title>
<issue_description>

DA-utils/src/ioda-dump/ioda-dump.h

Line 87 in 9113c30

throw eckit::Exception("Missing 'Shared Path' in YAML configuration");

This is only used when you are reading BUFR or ODB files, so we should make it optional and not fail if the input YAML does not define it. Perhaps the default value can be ./ and instead of throwing an exception, a warning is printed out that says it is not defined and will assume the path is the runtime directory?</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Shared Path should be optional #68

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[HyundeokChoi-NOAA]

This looks good. The shared path isn’t required for netCDF files.