fix: survive malformed provider config at startup

Eight config shapes, all valid TOML, crashed config.load() before any
window existed, so the user got a traceback on a terminal a desktop
launch does not have. Skip malformed providers instead, keeping the
local path working, and say on stderr which one was dropped and why.

The guards are isinstance tests rather than a try/except because the
shapes raise three different exception types, and the local entry is
checked the same way: [[providers.local]] is a truthy list that raised
during the bare base_url merge, before the loop could skip it.

A config that cannot load at all now reports the file and exits rather
than half-starting on defaults the user never configured.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0176tzAW6H1i2Kz8vm2XXVGV

0 files changed, 0 insertions, 0 deletions