firestore-bigquery-export kit: EXCLUDE_OLD_DATA and USE_NEW_SNAPSHOT_QUERY_SYNTAX read 'yes' as false

[cabljac]

The extension declared EXCLUDE_OLD_DATA and USE_NEW_SNAPSHOT_QUERY_SYNTAX as yes/no selects (firestore-bigquery-export/extension.yaml) and read them with === "yes" (functions/src/config.ts:195-196). The kit declares both with defineBoolean (kits/firestore-bigquery-export/src/config.ts:400 and :407), and firebase-functions' BooleanParam resolves the env var by comparing it to the string true (lib/params/types.js).

So a .env carried over from the extension with EXCLUDE_OLD_DATA=yes silently reads as false: old_data is written where the extension omitted it. USE_NEW_SNAPSHOT_QUERY_SYNTAX=yes likewise reads as false, so the latest-snapshot view is created with the legacy syntax.

The README documents the rename ("change any yes to true in your .env"), so this is a known divergence, but it is silent at runtime and is not recorded on the parity tracker.

Options:

1. Read both via defineString with validationRegex: /^(true|false|yes|no)$/ and map yes to true, so a migrated .env keeps working.
2. Keep defineBoolean but add a validationRegex that rejects yes/no at deploy, so the mismatch fails loudly instead of flipping behaviour.
3. Keep as is and record the decision on Kits parity issues #2974.

1 is the parity choice. Tracked in #2974.