Problem

Mudlet currently does not handle telnet://host[:port] URLs passed via the command line. This prevents OS URL handlers from launching Mudlet and connecting when a user clicks a telnet link.

Proposed Changes

• Add a small telnet:// URL parser (TStringUtils::parseTelnetUrl) that validates scheme, host, and optional port (defaults to 23).
• Extend CLI positional argument parsing to detect a telnet URL and prioritize a matching profile (host+port), otherwise create a minimal new profile and connect.
• Add a QtTest regression test suite covering valid and invalid inputs.
• Make functional-test sanitizer include optional when building tests standalone (so unit tests can run without full build tree).

/claim #689

Proof

Local unit test run (macOS arm64, Qt 6.10.2):

• cmake -S test -B /tmp/mudlet-689-test
• cmake --build /tmp/mudlet-689-test --target TStringUtilsTelnetUrlTest
• /tmp/mudlet-689-test/TStringUtilsTelnetUrlTest

Output is attached in proof_689_tests.txt.

Checklist

• Added tests
• Included proof