[Bug] RAM check silently undercounts a multimodal model's footprint if mmprojSizeBytes is missing #70

Problem

RamCheckService._combinedSizeMb (lib/core/services/ram_check_service.dart:18) silently falls back to 0 when a multimodal model's mmprojSizeBytes is null, undercounting its true memory footprint.

Failure scenario

A future or sideloaded multimodal catalog entry that sets mmprojFilename but omits mmprojSizeBytes would have isLargeModel() skip the RAM-warning dialog, letting a genuine OOM during load surface as a raw native exception instead of the friendly "not enough free memory" message (#25).

Not reachable with today's two curated multimodal entries (Gemma 4 E2B/E4B, #22) — both fields are always set together — so this is latent/dormant rather than a live bug, and the surrounding code already acknowledges the gap in comments. Filed so it doesn't get missed if a future catalog entry (e.g. Bonsai 27B, #23) or a sideloaded model omits the size.

Found during v1.2.0 release-readiness code review of the main...develop diff.

Fix direction

Either require mmprojSizeBytes whenever mmprojFilename is set (validate at catalog/parse time), or have _combinedSizeMb treat a missing size as "unknown" (triggering the warning path conservatively) rather than 0.