Detail exchange and merge

Detail exchange uses the independent version llm-usage-details-1. It preserves complete normalized events, per-field quality, original host/source identity, source revisions, conflict flags and independent cumulative snapshots. Aggregate exchange remains compatible. Settings offers separate aggregate/detail exports; import detects the package format and previews scope/counts before execution. Exports contain only the statistical allowlist, excluding conversation bodies, credentials, additional original-file path fields and collection cursors. Stable source keys remain unchanged. Both import and export use a 64 MiB limit so an exported package is not too large to import again.

Detail packages include sealed day/hour/period partitions. Source days with retained details are recomputed from events without adding exported summaries. Details and sealed snapshots for the same source day cannot overwrite each other; incomplete details cannot unseal an old snapshot. Cumulative snapshots retain exclusive/duplicate/overlap_unknown and are not expanded into individual calls. Exports validate complete source days; a target source day containing only aggregates cannot be partially reconstructed. Original event costs stay with details; when estimation is enabled, affected unsealed days are recomputed in the same transaction. Database backups preserve price snapshots, application cost caches and system configuration; a details package is not a whole-database backup.

Import preserves source IDs; matching paths on different hosts do not merge. Sources default to disabled and the default user. Explicit import does not change original attribution. Per-request records retain source keys and source revisions. When both records have revision numbers, compare those numbers; otherwise compare lifecycle order (partial < final < corrected). A higher rank replaces the existing record, a lower rank keeps it, and equal ranks with different content retain the existing record and conflict history. Identical records are skipped. An absent package record has no deletion meaning. Incomplete per-request exports from old formats can only be imported as aggregate packages; field quality is not fabricated.

Source registration, events, cumulative data, archives and summaries commit in one SQLite transaction. Any invalid field, attribution conflict or failure rolls back the entire batch. The retention floor is respected, removed details are not restored, and duplicate imports do not advance the usage revision. Processing positions/cursors are not imported; subsequent local collection continues from its own positions.

Validation covers nonempty round trips, unknown fields, duration/cost/quality/model attribution, cumulative data and archives, exclusive additions, source-revision replacement, conflicts, repeat reads, cross-host rejection, retention floors, whole-batch rollback and real IPC.