Docs: CATALOG.md never mentions `curate --sql-file` and lacks a catalog-root troubleshooting entry

Two small gaps in CATALOG.md: a real `curate` flag the reference never mentions, and no troubleshooting entry for the error newcomers are most likely to hit. ## 1. `curate --sql-file` is undocumented - The flag exists: `src/hflow/cli.py:57-61` ("read the SELECT from a file instead of the command line"); the positional `sql` is optional (`nargs="?"`, line 52); passing both or neither prints `curate: pass exactly one of a SQL string or --sql-file` and exits 2 (`src/hflow/cli.py:487-489`). - The docs never define it: the CLI example in `docs/CATALOG.md:72-77` shows only inline SQL. Meanwhile `examples/egocentric/README.md:79-83` uses `--sql-file`, so a reader meets the flag in an example before any reference explains it. - Fix: extend the CATALOG.md CLI section with `--sql-file` and the exactly-one rule. ## 2. No troubleshooting entry for "is not a catalog root" - `src/hflow/curation.py:115-119` raises `" is not a catalog root (no format_version marker); expected the location a Catalog was created with, e.g. /catalog"`. This fires whenever `--catalog` points at the data root instead of `/catalog`, an easy first mistake. - Fix: a two-line troubleshooting note in CATALOG.md saying what the error means and what to pass instead. ## Pattern to copy The existing CLI block and prose style in `docs/CATALOG.md`; the troubleshooting entry style in `docs/RUNTIME.md` (its "Port 8080 is taken" entry). ## Definition of done - CATALOG.md documents `--sql-file`, the exactly-one rule, and the catalog-root error. - Line numbers above are from current main; re-check them before editing. ## Validation ```bash lychee --no-progress --include-fragments \ --exclude '^https://github\.com/Hebbian-Robotics/hflow/(issues|security/advisories/new)$' \ --exclude-path references/mcap-spec.md \ --exclude-path references/foxglove-CompressedVideo.proto . ```