Update inspect and contracts tooling for structure slots features

Update refrakt inspect and refrakt contracts to surface the new SPEC-033 features: slot assignments, projection effects, and repeated elements.

Acceptance Criteria

refrakt inspect output shows slot assignments when a rune config declares slots
refrakt inspect visualizes projection effects (shows before/after tree when projection is active)
refrakt inspect --audit flags new BEM selectors created by projection group entries
refrakt contracts includes slot ordering in structure contracts
refrakt contracts includes projection declarations and warns on invalid data-name references (targeting a data-name that doesn't exist in the rune's output)
refrakt contracts --check catches drift from slot/projection changes
All existing CLI tests pass

Update the inspect renderer to show slot groupings in the HTML output
Add projection visualization — when projection is configured, show the tree before and after the projection pass
Update the contracts generator to include slot order and projection declarations in the JSON output
Add validation for projection data-name references against the rune's known output contract
Update the audit logic to account for group-generated BEM selectors