database.toml lookup_tables list not updated when a lookup table is removed from schema.yaml

**Where:** No skill currently instructs checking `database.toml`'s `lookup_tables` array when a table is removed from `schema.yaml`. The astrodb-build-schema-generate skill (and the general "modify schema.yaml" workflow) only mentions Felis YAML edits.

**What happened:** After removing `AssociationList` and `CompanionList` from `schema.yaml` (dataset had no data for those tables), `database.toml` still listed them under `lookup_tables`. This wasn't caught by Felis validation (`Schema.model_validate()` passed fine) since `database.toml` isn't part of the Felis schema — it's a separate astrodb_utils config file. It would have surfaced later as a confusing error when `build_db_from_json()` tried to load a nonexistent table.

**Workaround:** Manually grepped `database.toml` for the removed table names and edited the `lookup_tables` list by hand.

**Suggested change:** Any skill instructions covering schema.yaml table removal/renaming should add a step: "grep `database.toml`'s `lookup_tables` array for the removed/renamed table name and update it to match."

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_Reported from a gotchas.md log filed by a skill user (2026-08-28)._

Locate the astrodb-build-schema-generate skill and the general “modify schema.yaml” workflow instructions, then read how table removals and renames are currently described. Update those instructions to check database.toml’s lookup_tables array against schema.yaml; the work is done when removed or renamed table names are explicitly covered.

Written by the indexing model from the issue text.