feat: Phase C C8 benchmark deprecation banner system -- prevents stale benchmark authority

docs/evidence/METRICS_CURRENT.md

@@ -9,6 +9,15 @@ Machine-readable snapshot: `outputs/metrics_snapshot.json` regenerated with `mak
 
 ## Changelog
 
+### v0.10.35 — Phase C C8: Benchmark deprecation banner system
+- Added `src/openamp_foundry/evidence/benchmark_deprecation.py`
+- Functions: get_deprecated_cards(), get_active_cards(), build_deprecation_banner(), print_all_deprecation_banners(), check_no_deprecated_in_ranking() (raises DeprecatedBenchmarkError), deprecation_status_report()
+- DeprecatedBenchmarkError: raised when deprecated benchmarks are used in ranking context
+- Main registry confirmed: all 5 BMC- cards are active (no deprecated)
+- 63 tests in `tests/evidence/test_benchmark_deprecation.py`
+- BASELINE 6772→6835
+- Closes Phase C C8 — stale benchmark authority is now machine-preventable via check_no_deprecated_in_ranking()
+
 ### v0.10.34 — Phase C C1: Machine-readable benchmark registry
 - Added `src/openamp_foundry/evidence/benchmark_registry.py` — benchmark card registry
 - 5 BMC- cards: BMC-0001 (precision@k, leakage_aware_split), BMC-0002 (charge-matched, charge_stratified), BMC-0003 (calibration, random_70_30), BMC-0004 (family-stratified, family_stratified), BMC-0005 (cheap enemy comparison, leakage_aware_split)

docs/research/NEXT_100_PR_MAP.md

@@ -65,7 +65,7 @@ Make OpenAMP the hardest repo to fool in AMP dry-lab selection.
 | C5 | Add `bench-length-matched` control. | Tests length shortcut. | C |
 | C6 | Add `bench-charge-length-matched` control. | Stronger nontrivial signal test. | C |
 | C7 | Add family-stratified precision@k. | Helps panel design. | C |
-| C8 | Add benchmark-deprecation banner system. | Prevents stale benchmark authority. | B |
+| C8 | Add benchmark-deprecation banner system (complete). | benchmark_deprecation.py: get_deprecated_cards(), build_deprecation_banner(), check_no_deprecated_in_ranking() (raises DeprecatedBenchmarkError), deprecation_status_report(); 63 tests; main registry confirmed all-active. | B |
 | C9 | Add command that compares all advanced scorers against declared cheap enemies. | Standardizes anti-hype. | C |
 | C10 | Add benchmark governance CI that rejects missing benchmark cards for new benchmark scripts. | Prevents benchmark sprawl. | B/C |
 

src/openamp_foundry/evidence/benchmark_deprecation.py

@@ -0,0 +1,140 @@
+"""Benchmark deprecation banner system — Phase C C8.
+
+Prevents stale benchmark authority by providing:
+1. Detection of deprecated benchmark cards in the registry
+2. Human-readable deprecation banners for each deprecated card
+3. A strict governance check that fails if deprecated benchmarks are used
+   in official ranking decisions without explicit override
+
+Usage:
+    from openamp_foundry.evidence.benchmark_deprecation import (
+        check_no_deprecated_in_ranking,
+        get_deprecated_cards,
+        build_deprecation_banner,
+        print_all_deprecation_banners,
+    )
+
+    # In CI or ranking pipeline:
+    check_no_deprecated_in_ranking(registry)  # raises if any card is deprecated
+
+    # For user-facing warnings:
+    print_all_deprecation_banners(registry)
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from openamp_foundry.evidence.benchmark_card import BenchmarkCard
+
+_BANNER_WIDTH = 72
+_BANNER_CHAR = "!"
+
+
+class DeprecatedBenchmarkError(Exception):
+    """Raised when a deprecated benchmark is used in a ranking context."""
+
+
+def get_deprecated_cards(
+    registry: list["BenchmarkCard"],
+) -> list["BenchmarkCard"]:
+    """Return all deprecated BenchmarkCards from the given registry."""
+    return [card for card in registry if card.deprecated]
+
+
+def get_active_cards(
+    registry: list["BenchmarkCard"],
+) -> list["BenchmarkCard"]:
+    """Return all non-deprecated BenchmarkCards from the given registry."""
+    return [card for card in registry if not card.deprecated]
+
+
+def build_deprecation_banner(card: "BenchmarkCard") -> str:
+    """Build a human-readable deprecation banner for a deprecated benchmark.
+
+    The banner is designed to be impossible to miss: it uses a visible
+    header, states the benchmark ID and name, and quotes the notes field
+    which must explain the deprecation reason.
+    """
+    sep = _BANNER_CHAR * _BANNER_WIDTH
+    lines = [
+        sep,
+        f"DEPRECATED BENCHMARK — {card.bmc_id}",
+        sep,
+        f"Name:    {card.benchmark_name}",
+        f"Target:  {card.measurement_target}",
+        f"Reason:  {card.notes or '(no reason given)'}",
+        sep,
+        "WARNING: This benchmark is DEPRECATED and must NOT be used to make",
+        "ranking decisions or support candidate selection claims.",
+        "Remove or replace it before publishing results.",
+        sep,
+    ]
+    return "\n".join(lines)
+
+
+def print_all_deprecation_banners(
+    registry: list["BenchmarkCard"],
+) -> list[str]:
+    """Print deprecation banners for all deprecated cards.
+
+    Returns the list of banners printed (useful for testing without capturing stdout).
+    """
+    deprecated = get_deprecated_cards(registry)
+    banners: list[str] = []
+    for card in deprecated:
+        banner = build_deprecation_banner(card)
+        print(banner)
+        banners.append(banner)
+    return banners
+
+
+def check_no_deprecated_in_ranking(
+    registry: list["BenchmarkCard"],
+    allow_deprecated: bool = False,
+) -> None:
+    """Strict governance check: raise if any deprecated benchmark is in the registry.
+
+    Args:
+        registry: List of BenchmarkCard instances to check.
+        allow_deprecated: If True, skip the check (for testing only — must be
+                          documented in code review).
+
+    Raises:
+        DeprecatedBenchmarkError: If any card in the registry is deprecated.
+    """
+    if allow_deprecated:
+        return
+
+    deprecated = get_deprecated_cards(registry)
+    if deprecated:
+        names = ", ".join(f"{c.bmc_id} ({c.benchmark_name!r})" for c in deprecated)
+        raise DeprecatedBenchmarkError(
+            f"Deprecated benchmarks found in ranking registry: {names}. "
+            "Remove deprecated cards from the registry before running official "
+            "ranking. Set allow_deprecated=True only in test contexts with "
+            "explicit code-review approval."
+        )
+
+
+def deprecation_status_report(
+    registry: list["BenchmarkCard"],
+) -> dict:
+    """Return a machine-readable deprecation status report for the registry.
+
+    Returns a dict with:
+        total: int — total cards in registry
+        active: int — non-deprecated cards
+        deprecated: int — deprecated cards
+        deprecated_ids: list[str] — BMC IDs of deprecated cards
+        all_active: bool — True if no deprecated cards
+    """
+    deprecated = get_deprecated_cards(registry)
+    return {
+        "total": len(registry),
+        "active": len(registry) - len(deprecated),
+        "deprecated": len(deprecated),
+        "deprecated_ids": [c.bmc_id for c in deprecated],
+        "all_active": len(deprecated) == 0,
+    }