DRB-8: Unify bench/ E5 and perf/ schema-v2 performance authority

[metaphorics]

Problem

Two live performance policy surfaces coexist and contradict each other. The repository must decide whether they are deliberately separate evidence tracks or one supersedes the other, then assign a single non-conflicting owner for host conditions, argv model, baselines, thresholds, and artifact directories.

Exact conflicts

• Host conditions: bench/compiler-rules.toml:20-32 requires performance governor, disabled swap, and pinned affinity (schema bamti.compiler-rules/v1). perf/hosts/bh1.toml:24-30 records powersave governor, swap_total_kib = 403979000, and affinity 0-19 (schema = 2). These are mutually exclusive default host profiles.
• Baseline directories: bench/compiler-rules.toml:139 expects bench/baselines/stage1.json; perf/benchmarks.toml:15,26,36,46,56,66,76,86,96,106,116,127 expects perf/baselines/s0.json..s11.json.
• Argv model: bench/compiler-rules.toml:58-68,76-78,90-98,105-112,137-138 uses runtime flags like ["-r", "--jit", "--json"]. perf/benchmarks.toml:185 uses ["check", "{fixture}"], which conflicts with docs/reference/cli.md:65 (the previous check interface is not part of the current public CLI).
• Consumers: Cargo.toml:11-21 registers bench/jit_benchmarks.rs, bench/stage0_evidence.rs, and bench/stage1_regression_guard.rs; crates/bamts-verification/src/lib.rs:24-26 and main.rs:165 wire perf_stage0, perf_jit, perf_guard; crates/bamts-verification/src/bin/perf_budget.rs consumes schema-v2 perf/hosts/bh1.toml. verification/catalog-inputs.json and completion-program.toml:937-973 lock E5 leaves to bench/ paths.

Scope of change

• Decide whether bench/ (E5) and perf/ (schema-v2 / PB-1 / BH1) are distinct tracks with non-overlapping host IDs, or whether one schema is the migration target.
• If distinct, document the boundary: which measurements, gates, binaries, and CI lanes use which surface, and ensure no gate mixes the two policies.
• If unified, pick the surviving schema, migrate all consumers, baselines, thresholds, manifests, and CI/completion references, then archive the superseded surface.

Source-of-truth predecessors

• Host conditions: the chosen single policy manifest (bench/compiler-rules.toml, perf/hosts/bh1.toml, or a merged perf/policy.toml).
• Baseline/scorecard paths: the surviving surface's manifest + perf_budget / bamts-verification consumers.
• Argv content reconciliation: DRB-3 (CLI contract drift) owns whether check is a public or internal-only command.
• Missing baselines: DRB-12.

Acceptance

• grep across Cargo.toml, crates/, verification/, .outline/gates/, Justfile, and .github/workflows/ shows no mixed references to both bench/compiler-rules.toml and perf/hosts/bh1.toml for the same measurement gate.
• One and only one named file owns host conditions, argv model, baseline paths, and thresholds for each active performance leaf.
• cargo check and cargo test -p bamts-verification pass with the chosen single surface (or with explicitly separated E5/PB host IDs and distinct binary entry points).
• perf_budget / bamts-verification perf_* emits a deterministic error (not silent policy picking) when host conditions or required baselines are missing.

Blockers

• DRB-3 (CLI contract drift) for the argv = ["check", ...] content.
• DRB-12 (missing planned artifacts) cannot classify baselines until this decision is made.

[metaphorics]

Dependencies

This issue is blocked by:

• Audit documentation rules and build surfaces #163 — Audit documentation rules and build surfaces (docs-rules-build-audit source)
• Set performance budgets and trade-off authority #170 — Set performance budgets and trade-off authority (dual perf authority decision)
• [DRB-3] Reconcile CLI docs against parser and dispatch evidence #191 — [DRB-3] Reconcile CLI docs against parser and dispatch evidence (owns whether check is a public or internal-only command — argv content reconciliation)

DRB-12 (#198) cannot classify baselines until this decision is made — but DRB-8 does NOT depend on DRB-12. The ordering is DRB-8 → DRB-12, not circular.

Parent: #156. Feeds: #185.