testing: rekey settle past drain window + stale tooling references

- testing/static/scripts/rekey-test.sh: bump REKEY_SETTLE from 5s to
  12s so post-rekey ping_all samples are taken after the 10s old-
  session drain window has closed (DRAIN_WINDOW_SECS in
  handlers/rekey.rs). The 5s sample window straddled the drain,
  occasionally catching old-session decrypts mid-cutover and producing
  spurious ping failures.

- testing/lib/log_analysis.py: discovery-succeeded match string is
  "proof verified, route cached" (the wording in handlers/discovery.rs);
  the regex looked for the older "caching route" wording, so the chaos
  analysis summary always reported `Succeeded: 0` regardless of how
  many successes the raw node logs actually showed.

- testing/scripts/build.sh: drop the second cargo invocation that
  passed `--features gateway --bin fips-gateway`. PR #79 removed the
  `gateway` cargo feature in favor of platform cfg gates, so this
  invocation now fails with `the package 'fips' does not contain this
  feature: gateway`. The first cargo build already produces
  fips-gateway as a workspace binary on every supported target.

testing/scripts/build.sh

@@ -46,13 +46,11 @@ if [ "$UNAME_S" = "Darwin" ]; then
 
     echo "Building FIPS for Linux (release) using cargo-zigbuild..."
     cargo zigbuild --release --target "$CARGO_TARGET" --manifest-path="$PROJECT_ROOT/Cargo.toml"
-    cargo zigbuild --release --target "$CARGO_TARGET" --manifest-path="$PROJECT_ROOT/Cargo.toml" --features gateway --bin fips-gateway
 
     TARGET_DIR="$PROJECT_ROOT/target/$CARGO_TARGET/release"
 else
     echo "Building FIPS (release)..."
     cargo build --release --manifest-path="$PROJECT_ROOT/Cargo.toml"
-    cargo build --release --manifest-path="$PROJECT_ROOT/Cargo.toml" --features gateway --bin fips-gateway
 
     TARGET_DIR="$PROJECT_ROOT/target/release"
 fi