Add Threadlight trailer beatboard

[RollNuts]

Summary

• Adds a 30-second trailer beatboard built from the Threadlight world-contact-sheet assets.
• Uses no additional image generation; the beatboard is cut from Add Threadlight world contact sheet #19 assets.
• Records visual QA: v1 opening crop placed the surveyor too low; v2 restores the role read and is the review target.

Review Path

• Primary review image: docs/art/threadlight/threadlight-trailer-beatboard-v2.png
• Notes: docs/art/threadlight/trailer-beatboard.md

Trailer Promise

The first 30 seconds should sell: lantern finds route, light reveals threat, thread binds action, threat pushes back, caravan payoff, boss landmark wakes, readable combat peak.

Validation

• Visual inspection performed on v1 and v2 beatboards.
• git diff --check passed.
• Local docs-gate equivalent passed.

Stack

Base PR: #19 (art/world-contact-sheet)
Parent PR: #18 (research/character-pipeline-and-video-tools)
Next step should be choosing one low-cost 3D preview target: threadlight route tool or light-moth enemy.

[RollNuts]

Veripsa review note: this is a stacked trailer-planning PR on top of #19.

Scope: adds threadlight-trailer-beatboard-v2.png and notes. It uses no additional image generation; it cuts the #19 world-contact-sheet assets into a 30-second store-facing trailer structure.

Review target: does the sequence sell role + world rule + hub payoff + boss landmark before UI/loot/full hero production? QA note: v1 opening crop placed the surveyor too low; v2 is the adopted version because it restores the player role read in the first 3 seconds.

Recommended order: #18 market/world definition -> #19 world contact sheet -> #20 trailer beatboard.