`streamd daily [YYYYMMDD]` opens the earliest existing daily file
(file_type=daily) whose timestamp falls within the target date.
If no such file exists it creates `<timestamp>_daily.md` and opens it.
Date defaults to today in the repository timezone.
Add `extract_file_type_from_file_name` to parse prefixes like `_daily`
from filenames (e.g. `20260412-123456_daily.md` → `"daily"`).
Insert the result into `initial_location` in `localize_stream_file` so
all localized shards carry a `file_type` dimension value.
Also register the `file_type` dimension in `TaskConfiguration` so the
propagation contract is documented.
