fix(etl): persist DDEX rights metadata on track create

[rickyrombo]

What

mergeTrackFromMetadata (the update path) has read these eight fields for a
while. The create INSERT never listed them:

artists, resource_contributors, indirect_resource_contributors,
rights_controller, copyright_line, producer_copyright_line,
parental_warning_type, is_original_available

A track that arrives complete in a single Create silently loses all eight.

Why the migration hits it every time

Every genesis-migration track is exactly that shape — one Create, never
updated. The writer selects and emits these fields
(cmd/genesis-writer/entities_track.go), the transaction carries them, and the
row lands with NULLs.

Verified end to end on track 1810289900:

source tracks.rights_controller     {"name": "Michael Kumar", "roles": ["RightsController"]}
migration tx data.rights_controller {"name": "Michael Kumar", "roles": ["RightsController"]}   <- writer did its job
ETL tracks.rights_controller        NULL                                                      <- dropped here

Measured loss (2026-08-07 snapshot)

column	rows lost
is_original_available	28,827
producer_copyright_line	1,459
parental_warning_type	1,459
artists	1,447
rights_controller	1,404
indirect_resource_contributors	782
copyright_line	782
resource_contributors	686

Test

TestTrackCreate_PersistsDdexRightsMetadata uses metadata shaped as
genesis-writer emits it. Reverting the fix fails it on all four assertions:

artists is empty; the create INSERT dropped it
rights_controller is empty; the create INSERT dropped it
parental_warning_type = <nil>, want "Explicit"
is_original_available = false, want true

🤖 Generated with Claude Code