fix(init): report a malformed --extension URL cleanly, not raw urllib text

[Noor-ul-ain001]

Summary

• _install_extension_during_init (src/specify_cli/commands/init.py) parses an --extension URL spec with a bare parsed = urlparse(ext_spec).
• An unterminated or invalid bracketed IPv6 authority (e.g. https://[not-an-ip]/x.zip) makes urlparse() itself raise ValueError — this became eager in Python 3.14 (previously lazy, raised only on .hostname access). Since the call was unguarded, specify init --extension <bad-url> surfaced the raw urllib message ('not-an-ip' does not appear to be an IPv4 or IPv6 address) as the tracker's failure text instead of an actionable error.
• Every sibling URL entry point in this codebase already guards this exact case with a clean domain error: extensions/__init__.py, presets/__init__.py, extensions/_commands.py, workflows/catalog.py (the #3435/#3484 lineage — each has an explicit comment about this). init.py's own _ext_spec_is_url classifier, defined right next to this function, already catches the same ValueError; this call site was the one outlier that didn't.
• Fix: wrap the parse in the same try/except ValueError pattern as every sibling, raising a clean ValueError("Malformed extension URL: ...") that the caller already converts into a tracker error (per this function's own documented contract).

Test plan

• Added test_install_extension_during_init_reports_malformed_url_cleanly to tests/test_init_output_markup.py, calling _install_extension_during_init directly with https://[not-an-ip]/ext.zip.
• Verified the test fails without the fix — reproduced the exact raw urllib message ('not-an-ip' does not appear to be an IPv4 or IPv6 address) leaking through — and passes with it.
• Ran the full tests/test_init_output_markup.py module — 9 passed, 3 skipped (pre-existing bash-requirement skips), no regressions.

Co-Authored-By: Claude Sonnet 5 noreply@anthropic.com
Claude-Session: https://claude.ai/code/session_01FW9fAYsCBCAgdKWovtSyqt