Add comprehensive tests for cstringstream.c achieving 95.5% line coverage

[Copilot]

Adds test coverage for src/cstringstream.c to meet the 90% coverage target.

Coverage Results

• Line coverage: 95.5% (85/89 lines)
• Function coverage: 100% (16/16 functions)
• Uncovered lines are malloc failure paths (lines 68-69, 93-94)

Tests Added

• Creation/deletion: newStringStream, deleteStringStream with NULL handling
• Stream operations: clearStringStream, copyStringStream, resizeStringStream
• Accessors: sizeStringStream, getStringStream, putStringStream
• Append functions: char, string, int, unsigned, long, unsigned long, double
• String extraction: stringFromStringStream
• Edge cases: NULL parameters, invalid indices, resize triggers, empty streams

TEST_CASE("cstringstream - appendStringStringStream", "[cstringstream]") {
    SECTION("Append string") {
        cstringstream ss = newStringStream();
        REQUIRE(appendStringStringStream(ss, "Hello") == 0);
        REQUIRE(appendStringStringStream(ss, " World") == 0);
        
        char *str = stringFromStringStream(ss);
        REQUIRE(strcmp(str, "Hello World") == 0);
        
        free(str);
        deleteStringStream(ss);
    }
    
    SECTION("NULL stream returns -1") {
        REQUIRE(appendStringStringStream(nullptr, "test") == -1);
    }
}

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• esm.ubuntu.com
  • Triggering command: /usr/lib/apt/methods/https /usr/lib/apt/methods/https (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

Complete test cases for src/cstringstream.c and target 90% coverage for the source file.

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