fix: skip unusable provider names, name the split ceiling

A provider name containing a colon builds ids that split back to a
different provider, and an empty name builds ':model'; both routed to the
local router under a nonsense name with no error, so parse() now skips
them. split() stays non-injective by design, since bare local ids are the
premise here, so the residual risk is recorded as a ponytail comment with
its upgrade path rather than hidden. Also pin the trailing-colon form Task
9 relies on, and the empty-needle filter, which were correct but untested.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

0 files changed, 0 insertions, 0 deletions