fix(build): include <ostream> in io_config.hpp

[daeho-ro]

Issue

There is no separate issue: include/storage/io_config.hpp fails to compile against libc++ 23, which no longer provides the transitive includes the header relies on.

IOConfig::ListInputFiles writes into a std::ostream, but the header includes only <array>, <filesystem>, <set>, <string> and <vector>. Up to libc++ 22 one of those pulled in <ostream>; libc++ 23 removed the transitive includes, so the operator<<(std::ostream&, const char*) overload is no longer declared:

include/storage/io_config.hpp:53:21: error: invalid operands to binary expression ('std::ostream' (aka 'basic_ostream<char>') and 'const char[10]')
   53 |                 out << "required " << file.string() << "\n";
      |                 ~~~ ^  ~~~~~~~~~~~

This showed up when building v26.9.0 with Homebrew's clang/libc++ 23 on macOS; the same header in v26.8.0 has the problem too, it just did not surface with libc++ 22.

The fix is to include <ostream> directly.

Tasklist

• self-review code for correctness and following the coding guidelines
• add tests (not applicable: missing-include fix, covered by compiling the existing sources)
• update relevant wiki pages (not applicable)
• review
• adjust for comments

Verification

Built v26.9.0 with the patch using clang/libc++ 23 (arm64 macOS): all targets compile and all eight osrm-* binaries link. Without the patch the same build fails with the error above.

AI disclosure

An AI tool (Claude Code) was used to diagnose the failure and prepare this one-line change; the diagnosis and the resulting build were verified locally before submitting.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.80%. Comparing base (9e87315) to head (fb0251f).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7714      +/-   ##
==========================================
+ Coverage   91.91%   94.80%   +2.89%     
==========================================
  Files         526      526              
  Lines       42085    42085              
==========================================
+ Hits        38682    39899    +1217     
+ Misses       3403     2186    -1217     

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[DennisOSRM]

Thanks so much for the contribution