docs: streamline tone across reference docs

Tone pass across the non-tutorial markdown — README, PROOFS,
ARCHITECTURE, BENCHMARKS, COMPLIANCE, FAQ, MES_INTEROP, SECURITY,
and interop/README.  Three patterns came out:

- Bug-history war stories ("Past interop sweeps surfaced…",
  "What these harnesses caught: 1. Strict U-width parsing…").
- Chat-with-reader framing ("Don't skip TLS unless…", "Treat as a
  punch list", "If you're running in a pod…", "Misconfiguration
  incidents drop dramatically").
- Self-referential narration ("we ship", "our codec", "the
  codebase's most-tested layer", "three orders of magnitude above
  fab load", "the gift that keeps giving").

README also drops the standalone ThreadSanitizer subsection under
Build details (now a single line under the new Testing section).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -48,21 +48,26 @@ through the data model.  Watch the logs interleave.
 
 ---
 
-## How it's proved
+## Testing
 
-"Feature-complete" is a claim that the code must prove, not the
-README.  On a fresh clone, **eight commands** demonstrate it:
-unit + integration suite (445 cases / 2 753 assertions), a live
-conformance harness (47 wire-level checks), interop against
-secsgem-py (31 checks) and secs4java8 (55 checks), a 100 000-op
-soak property test, YAML config validation, Wireshark's HSMS
-dissector on a recorded pcap (69 frames, 0 malformed), and libFuzzer
-(ASan + UBSan, 0 crashes).  Each command, exit code, and the
-external-vs-internal breakdown live in [docs/PROOFS.md](docs/PROOFS.md).
+- **Unit + integration** — `docker compose run --rm tests` runs 445
+  cases / 2 753 assertions across every store, FSM, codec, parser, and
+  persistence path.
+- **Live conformance harness** — 47 wire-level checks against the
+  passive server.
+- **Interop** — round-trips against secsgem-py (31 checks), secs4java8
+  (55 checks), and Wireshark's HSMS dissector (69 frames, 0 malformed).
+- **Soak + fuzz** — 100 000-op property test; libFuzzer with ASan +
+  UBSan over `secs2::decode` and the SML parser, 0 crashes.
+- **Config validation** — `secs_server --validate-config` rejects
+  malformed YAML before startup.
+- **CI** — [Gitea Actions](.gitea/workflows/ci.yml) runs the full
+  suite plus a `-fsanitize=thread` lane on every push to `main`; all
+  445 cases pass clean under TSan.
 
-CI runs the full suite plus a separate ThreadSanitizer lane on
-every push to `main` ([Gitea Actions](.gitea/workflows/ci.yml));
-all 445 cases pass clean under `-fsanitize=thread`.
+Exact commands, exit codes, and per-standard test counts are in
+[docs/PROOFS.md](docs/PROOFS.md); the rationale behind the external
+validators is in [docs/VERIFICATION.md](docs/VERIFICATION.md).
 
 ---
 
@@ -195,11 +200,9 @@ staging to a real tool.
 
 ## Deferred follow-ups
 
-- **asio `serial_port` adapter for SECS-I.**  The SECS-I FSM
-  (`secsi::Protocol`) is implemented and tested end-to-end over the
-  asio TCP transport (`secsi::TcpTransport`).  The serial driver —
-  a `serial_port` mirror of `TcpTransport`, a few hundred lines —
-  hasn't been written.  Mirror `TcpTransport` to add it.
+- **asio `serial_port` adapter for SECS-I.** `secsi::Protocol` is
+  tested end-to-end over `secsi::TcpTransport`; the matching serial
+  driver isn't written yet.  Mirror `TcpTransport` to add it.
 
 ---
 
@@ -213,17 +216,6 @@ live in a named Docker volume so the host filesystem stays clean.
 Standalone Asio is used in header-only mode (`ASIO_STANDALONE`).  No
 Boost dependency.
 
-### ThreadSanitizer
-
-```bash
-cmake -S . -B build-tsan -G Ninja -DCMAKE_BUILD_TYPE=Debug -DSECSGEM_TSAN=ON
-cmake --build build-tsan
-TSAN_OPTIONS=halt_on_error=1 build-tsan/secsgem_tests
-```
-
-Runs as a separate lane in CI.  Catches data races in the io_context
-strand contract documented in [docs/INTEGRATION.md](docs/INTEGRATION.md) §3.
-
 ---
 
 ## Interop
@@ -231,7 +223,7 @@ strand contract documented in [docs/INTEGRATION.md](docs/INTEGRATION.md) §3.
 Four independent external validators cross-check the codebase:
 
 - **secsgem-py 0.3.0** (Python reference impl) — three harnesses
-  under `interop/`: secsgem-py active host driving our C++ passive
+  under `interop/`: secsgem-py active host driving the C++ passive
   server (31 checks), C++ active host probing secsgem-py's passive
   equipment, and a raw GEM 300 harness round-tripping S3 / S14 /
   S16 / S12 through hand-crafted `SecsStreamFunction` subclasses.