🥇 [BR-OUTPUT] AlgorithmArena assembler (GOLD II) #460

Soul-name: Arena Anchor · Codename: LEAD · Priority: P2-MEDIUM · Kingdom: Rust
Ring: GOLD II trios-algorithm-arena / BR-OUTPUT
Part of: #446
Blocks: EPIC #446 acceptance (algorithm side)
Blocked by: SR-ALG-03 (issue 11) + at least 1 more SR-ALG ring shipped

Goal

Public-API assembler for GOLD II. Single function run_one(algo, seed) -> Bpb that picks a registered AlgorithmSpec, hands it to SR-02 TrainerRunner, and returns the validated BPB row id.

Acceptance criteria

• crates/trios-algorithm-arena/rings/BR-OUTPUT/ with I5 trinity.
• Public API: AlgorithmArena::register(spec: AlgorithmSpec), run_one(algo: AlgorithmId, seed: Seed) -> Result<BpbRowId, ArenaErr>, list() -> Vec<AlgorithmId>.
• Hash check (entry_hash) MUST pass before invocation (R-RING-DEP-002 enforcement).
• Integration test: register SR-ALG-03 e2e-ttt + SR-ALG-01 jepa stub, run_one returns BPB row id.
• PR closes this issue, Agent: LEAD trailer.

🌻 phi² + phi⁻² = 3