Add timeout-gated wait for `feed_is_live: trio.Event` before passing shm
tokens to `open_sample_stream()`; skip registering shm-buffers with the
sampler if the feed doesn't "go live" within a new timeout.
The main motivation here is to avoid the sampler incrementing shm-array
bufs when the mkt-venue is closed so that a trailing "same price"
line/bars isn't updated/rendered in the chart's view when unnecessary.
Deats,
- add `wait_for_live_timeout: float = 0.5` param to `manage_history()`
- warn-log the fqme when timeout triggers
- add error log for invalid `frame_start_dt` comparisons to
`maybe_fill_null_segments()`.
(this commit msg was generated in some part by [`claude-code`][claude-code-gh])
[claude-code-gh]: https://github.com/anthropics/claude-code