build_combined_prompt had a bug: when no anchor text was set, need_sep was
False for scene 1 so its text landed in Studio's segments[0] (anchor slot)
and never generated. An N-scene project with no anchor only produced N-1 scenes.
Fix: always emit a separator before every scene. Studio splits on separators,
so segments[0] is always the anchor (empty if no anchor text is set) and
segments[1..N] are the generated scenes. Fallback label is now "scene {i+1}"
(correctly numbered) instead of the previous "scene {label_n+1}" off-by-one.
Also: pass max_scenes = active scene count from the generate route into the
builder so the chain sampler always knows the exact number of scenes to produce.
Note on per-scene images: only the source image on scene 1 (project anchor
image) is wired to studio.source_image. Scene 2+ anchoring works via the
carry_i2v_guides flag on the chain sampler, which carries each scene's last
frame as the i2v source for the next scene. Per-scene i2v requires carry_i2v_guides
to be enabled in the sampler inspector — it is off by default.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
