Fix ACD export for non-program collection records

[astradzhao]

Summary

• ignore non-program metadata records beneath RxProgramCollection
• report missing or duplicate routine/tag collections with program context instead of an IndexError
• cover metadata filtering and collection diagnostics with focused SQLite tests

Test plan

• pytest test/test_program_collections.py test/test_elements_helpers.py -q
• full upstream suite: 68 passed, 2 skipped
• affected ACD converts to well-formed L5X while retaining valid programs, routines, and tags (local acceptance file not included)