feat: close 3-lang depth deck — same-turn roots, capability pins, public_demo budget
Complete residual work after PR #2/#3 merge:
- Same-turn he/grc depth via resolve_token_depths before PropGraph build
- Capability suite (he/grc exemplars, result fields, construction, dilation)
- public_demo: 60s reference budget, soft runtime case (hard raise opt-in)
- Pack-first geometric scale for fraction dilation; legacy N/M retained
- Re-pin public_demo SHA; lane-shas 9/9 green
Invariants: exact pack lookup, immutability, versor by construction, no
prior-turn dependency for first-contact he/grc root canonicalization.
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