[nosam1998]

Built-in model calls can now select a legal move through a reusable turn runner. Direct mode validates the action/reasoning object; tools mode offers current state, move selection, and only the planning assists allowed for the seat. The host binds planning to the same authorized service operations used by MCP and commits the selected move separately with a turn precondition.

Sessions preserve the immutable briefing, tool definitions, and signed conversation prefix. Reports retain every request/response, tool result, failed attempt, usage class, and elapsed time. Refusals, invalid moves, and invalid formats consume configured retries. Output tokens are capped across the entire move, the deadline includes planning calls, and sixteen provider calls bound endless tool loops. A tool batch selects at most one move and answers all remaining tool IDs. Transport/budget failures never silently retry or choose fallback actions.

Validation: all 27 provider/runner tests pass, including 12 scripted turn scenarios for recovery/exhaustion, signed-history round trips, forbidden assists, forged target fields, multiple moves, output/time limits, empty refusal completions, accounting, and uncertain provider failures. Clippy with warnings denied, formatting, and dependency-boundary checks pass.

This adds the player execution layer. Durable call reservations/journals and server seat scheduling remain a separate integration change; no paid model calls were made.

SemVer: additive feature (minor).