Resurrect dead Noise vector tests; add CI perf floors; make tests hermetic

Package.swift's .process("Noise") resource claim silently excluded all
of bitchatTests/Noise/ from compilation since Oct 2025 - including a
complete official-vector runner (cacophony + snow XX transcripts,
transport messages, handshake hash, byte-identical to upstream).
Narrowing the resource to the JSON file and loading via Bundle.module
brings 51 Noise tests back to life, with a guard asserting each
vector's protocol name matches the app's.

CI gains a performance floor gate: perf-floors.json carries deliberately
generous floors (~25% of measured throughput) that catch algorithmic
regressions without flaking on runner variance; PERF lines reach the
gate via an O_APPEND side-channel file since swift test --parallel
swallows passing tests' stdout.

Tests are now hermetic: FavoritesPersistenceService uses an in-memory
keychain under test (fixes the securityd hang that blocked pipeline
benchmarks locally) and read-receipt persistence uses a wiped scratch
UserDefaults suite instead of .standard.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/check-perf-floors.sh

@@ -0,0 +1,108 @@
+#!/usr/bin/env bash
+#
+# check-perf-floors.sh — order-of-magnitude performance regression gate.
+#
+# Parses the `PERF[name]: N unit/sec ...` lines that PerformanceBaselineTests
+# prints into captured test output and fails if any benchmark's throughput is
+# below its floor from bitchatTests/Performance/perf-floors.json.
+#
+# Floor philosophy (see the floors file): floors sit at ~25% of locally
+# measured throughput, so they catch algorithmic regressions (O(n) -> O(n^2)),
+# never runner variance. Raise floors deliberately after intentional
+# improvements; never tune them to chase noise.
+#
+# Usage: scripts/check-perf-floors.sh <test-output-file> [floors-file]
+#
+# Skips gracefully (exit 0) when:
+#   - BITCHAT_SKIP_PERF_BASELINES=1 (perf tests were skipped), or
+#   - the output contains no PERF lines (e.g. package-only matrix entries).
+#
+# Fails (exit 1) when:
+#   - any benchmark reports throughput below its floor, or
+#   - PERF lines are present but a floored benchmark is missing
+#     (a silently-dropped benchmark must be an explicit floors-file change).
+
+set -euo pipefail
+
+if [[ $# -lt 1 ]]; then
+    echo "usage: $0 <test-output-file> [floors-file]" >&2
+    exit 2
+fi
+
+OUTPUT_FILE="$1"
+FLOORS_FILE="${2:-$(cd "$(dirname "$0")/.." && pwd)/bitchatTests/Performance/perf-floors.json}"
+
+if [[ "${BITCHAT_SKIP_PERF_BASELINES:-}" == "1" ]]; then
+    echo "perf-floors: BITCHAT_SKIP_PERF_BASELINES=1 — skipping gate."
+    exit 0
+fi
+
+if [[ ! -f "$OUTPUT_FILE" ]]; then
+    echo "perf-floors: output file '$OUTPUT_FILE' not found — skipping gate." >&2
+    exit 0
+fi
+
+if [[ ! -f "$FLOORS_FILE" ]]; then
+    echo "perf-floors: floors file '$FLOORS_FILE' not found." >&2
+    exit 2
+fi
+
+if ! grep -q 'PERF\[' "$OUTPUT_FILE"; then
+    echo "perf-floors: no PERF lines in '$OUTPUT_FILE' — skipping gate."
+    exit 0
+fi
+
+OUTPUT_FILE="$OUTPUT_FILE" FLOORS_FILE="$FLOORS_FILE" python3 - <<'PYEOF'
+import json
+import os
+import re
+import sys
+
+output_file = os.environ["OUTPUT_FILE"]
+floors_file = os.environ["FLOORS_FILE"]
+
+with open(floors_file) as f:
+    floors = json.load(f)["floors"]
+
+# PERF[delivery.storeUpdate]: 158862 updates/sec (avg 3.147 ms per pass of 500, 10 passes)
+pattern = re.compile(r"PERF\[([^\]]+)\]:\s*([0-9]+(?:\.[0-9]+)?)\s*(\S+)/sec")
+
+measured = {}
+with open(output_file, errors="replace") as f:
+    for line in f:
+        m = pattern.search(line)
+        if m:
+            # Keep the last reported value if a benchmark prints twice.
+            measured[m.group(1)] = (float(m.group(2)), m.group(3))
+
+failures = []
+print(f"perf-floors: checking {len(measured)} benchmark(s) against {len(floors)} floor(s)")
+for name in sorted(set(floors) | set(measured)):
+    floor = floors.get(name)
+    if name not in measured:
+        failures.append(
+            f"  MISSING  {name}: floored benchmark reported no PERF line "
+            f"(removed/renamed? update perf-floors.json in the same change)")
+        continue
+    value, unit = measured[name]
+    if floor is None:
+        print(f"  NO-FLOOR {name}: {value:.0f} {unit}/sec (consider adding a floor)")
+        continue
+    status = "OK" if value >= floor else "BELOW"
+    line = f"  {status:8} {name}: {value:.0f} {unit}/sec (floor {floor})"
+    print(line)
+    if value < floor:
+        failures.append(
+            f"  BELOW    {name}: {value:.0f} {unit}/sec is under floor {floor} "
+            f"({value / floor * 100:.0f}% of floor)")
+
+if failures:
+    print("\nperf-floors: FAILED — order-of-magnitude-class regression suspected:")
+    print("\n".join(failures))
+    print("\nFloors are ~25% of healthy local throughput; falling below one means an")
+    print("algorithmic regression, not runner noise. If the change is intentional,")
+    print("update bitchatTests/Performance/perf-floors.json deliberately.")
+    sys.exit(1)
+
+print("perf-floors: all benchmarks at or above their floors.")
+PYEOF