Route FLUX.3 work and a third VIP picture to Fibo 2.0 - #278

Fibo 2.0 replaces FLUX.3 on aifarm-draw (iamwavecut/aifarm-draw#41, iamwavecut/aifarm-gpu-butler#15).

Routing (migration 212)

• Fibo 2.0 Edit Turbo (fibo_edit) takes every FLUX.3 edit assignment; Fibo 2.0 Dev (fibo_generate) takes every FLUX.3 text-to-image assignment, including the fallbacks of the Krea 2 and MOSS-Image slots. FLUX.3 is disabled.
• VIP draws get a third picture from the new image_generation_fibo workflow: Fibo 2.0 Dev primary, Krea 2 fallback, retry wall 240 s (a 50-step Fibo 2.0 Dev draw takes 100–120 s on GPU1).
• Every switched row records its previous model and every created row carries a marker, so the down migration restores the previous routing exactly. The migration does nothing unless the aifarm-draw provider, the GPU1 media pool, FLUX.3 and Krea 2 exist. Checked on a copy of the prod routing tables: up, a rerun stopped by the marker guard, and down back to the original rows.

Prompts

• New prompt target fibo (ImageModel::Fibo, 1600-char summary or instruction). When a slot targets Fibo 2.0, the generation and edit optimizers also return fibo_caption: a VGL caption (objects, background, lighting, aesthetics, photographic characteristics, style, text) whose short_description is the slot's prompt. The schema puts fibo_caption before outputs, so grammar-constrained JSON drafts the caption first.
• Only the Fibo 2.0 endpoints receive the caption; MOSS-Image keeps its layout, and a hop to another model sends the prose prompt alone. An edit sends the caption of the result, and draw-api adds the instruction as edit_instruction.
• Both optimizer prompts follow the Fibo 2.0 VGL guide; the edit optimizer names references as <image_1>, <image_2>, … the way Fibo 2.0 Edit reads them.
• One edit takes at most 4 references (was 10), in the draw tool, the dialog prompt and the reference selection.

Checks

• cargo fmt --all --check, cargo clippy --workspace --all-targets -- -D warnings
• cargo test -p openplotva-app -p openplotva-core -p openplotva-dialog -p openplotva-llm -p openplotva-media -p openplotva-storage: all pass.
• Fibo 2.0 worker smoke on a 4060 Ti: text-to-image at 1 MP in 96–121 s (50 steps), edits in 14–15 s with one reference, 21.5 s with two, 62 s with four.