Wizard focus-file frontend, scene edges, and timing fidelity

[jmjava]

Summary

Turns docgen wizard into a real focus-file frontend and ships continued graphics + timing improvements in the library.

Frontend (docgen wizard)

• Focus file picker scans Markdown and source types (.py, .yaml, .ts, …; configurable via wizard.scan_extensions)
• Save focus files writes durable context.paths into segment hint front matter (category B) and runs yaml-generate
• Production view adds a Focus files tab; regenerate narration uses those paths
• Pipeline buttons: timestamps, scene-spec (+ compile), then Manim / compose / validate

Graphics

• First-class scene-spec edges (from / to / optional palette color) → _arrow + GrowArrow
• Stronger _box / _arrow styling
• Scene-spec LLM prompt steers flow diagrams toward edges

Timing

• Pause-aware word weights (punctuation gets a small TTS breath share)
• Merge over-detected silence intervals toward sentence count for the 1:1 path
• Hyphen/underscore label tokenization (yaml-generate ↔ spoken yaml + generate) + soft long-token fallback

Other

• Pin [tool.ruff.lint] select = ["E4", "E7", "E9", "F"] so Ruff 0.16+ broader defaults do not fail CI on the existing tree

Test plan

• pytest tests/ (290 passed)
• ruff check src/ tests/
• Smoke: docgen wizard → select focus files → Save → confirm hint front matter + docgen.yaml merge
• Optional: scene-spec with edges: → scene-compile → Manim render shows arrows