Give every `maybe_open_price_feed()` caller a lexical child from the
cached `LinkedTaskChannel` broadcaster instead of yielding the raw
channel to the first owner and constructing competing roots for hits.
Add a concurrent regression proving miss and hit callers receive the
same quote, close independently, and leave the retained root alive.
Prompt-IO: ai/prompt-io/opencode/20260813T225940Z_b691422b_prompt_io.md
(this patch was generated in some part by `opencode` using `gpt-5.6-sol` (`openai`))
Gud Boi