#2171 Scene Workspace synchronization

[BryanHarrisScripts]

Closes #2171

What this changes

• converges the existing split Scene Timeline / progressive production views into one synchronized Scene Workspace
• projects current PPF screenplay Scene evidence when richer legacy Scene detail is unavailable, without making legacy localStorage authoritative
• preserves stable Scene, Block, Mini-Block, Shot and source-passage identities
• presents one workbench with screenplay source, rough/intent playback, cue inspector and Dialogue / Action / Shot / Audio lanes
• keeps Dialogue and Action screenplay-owned, Shot timing Previs-owned, and Audio Sequence Director / Sonic Cue-owned
• keeps unowned/un-timed source cues explicitly unplaced instead of manufacturing timestamps
• removes the old 75-second technical Mini-Block render preset from creative Scene Workspace timing
• synchronizes Scene Workspace span to the longest real authored timed cue
• keeps planned Shot duration edits on the existing Previs authority and protects approved timing behind the existing Provider-neutral Universal Creative Transaction Contract #2035 transaction path
• routes cue context back to current Block-native Write or forward to current Previs while preserving Block/Mini address
• replaces the old Scene Timeline WebMCP/visual selector with the Scene Workspace selector while retaining the stable internal registry key
• keeps the entire surface on current Skin V1 tokens, typography, controls, focus treatment and square geometry
• updates prior Matrix Reference Artifact Contract #2124/Pre-production Visual Story Workspace: Story Map → Visual Story → Scene Timeline #2125/Manual UAT: connect Outline → Storyboard → Visual Story → Previs as one coherent pre-production flow #2161 regressions to the converged product contract
• adds focused Scene Workspace: synchronize screenplay, playback, Dialogue / Action / Shot / Audio timeline #2171 regression coverage

Boundaries

• no Scene Workspace canon store
• no timeline-owned dialogue/action/audio
• no invented Scene, cue, media or timing
• no render-grid-derived creative timing
• no automatic approval
• no bypass of Provider-neutral Universal Creative Transaction Contract #2035 for approved Shot timing changes
• no alternate visual language or legacy route shell

Full verification is delegated to Architecture Verification on the exact PR head.