Fix dead code in IndexConfigBuilder::build() logic, and other issues

[hpdic]

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Reference Issues/PRs

What does this implement/fix? Briefly explain your changes.

This PR fixes a logical error in IndexConfigBuilder::build() where a safety check logic was duplicated, causing the logging code to become unreachable dead code. A couple of minor things: missing some header includes; string check is redundant.

Previously, there were two identical if (_dynamic_index && _num_frozen_pts == 0) checks.

The first check silently set _num_frozen_pts = 1.

The second check (which contained the warning log) would effectively become if (true && 1 == 0), which always evaluates to false.

As a result, the warning message "_num_frozen_pts passed as 0 ..." would never be printed.

The fix: I removed the first redundant check. Now the code correctly logs the warning before overriding the value to 1.

I also fixed a few other minor things like missing header includes and string checks.

Any other comments?