docs: bring the documentation up to the daemon/client era

A large gap had opened between the docs and the code: the README and
INTEGRATION guide did not mention the gRPC daemon or the Python client at
all (the entire vendor surface), ARCHITECTURE still described secs_server
as the ~1200-line canonical wiring example (it is a ~110-line thin main
over EquipmentRuntime), and test counts across six files were stale
(445/2753 -> 473/3087 core + the separate 125-assertion daemon suite).

- README: new "Integrating your tool (pick a tier)" section — Python
  client / any-language gRPC / embedded C++ — plus daemon tests and
  tools/run_interop.sh in the Testing section.
- ARCHITECTURE: layer diagram gains the vendor-surface and
  EquipmentRuntime/default_handlers tiers; stale wiring row fixed.
- INTEGRATION: three-tier chooser up front (this guide = the C++ tier).
- ch30 tour: secs_gemd + secs_gemd_tests in the binaries table.
- ch31: example alarm used a nonexistent `alcd:` field with bit 7 set
  (which the validator forbids) -> real `category:`/`name:` fields, and
  the roles: block documented.
- ch35: handler-location note now points at default_handlers.cpp's 15
  per-capability register_* functions.
- ch40: built-artifacts list + sample output counts.
- ch50: secsgem::gem runtime/default_handlers/handler_slot/name_index
  includes + new secsgem::daemon namespace section.
- PROOFS: test-count table gains the runtime/handlers/daemon row so the
  tally adds up; daemon suite noted. VERIFICATION/COMPLIANCE counts.
- interop/README: the one-command runner + the two daemon-track harnesses
  (daemon_interop, pyclient_interop).

Audited via a docs-vs-code sweep (the audit itself under-reported: it
validated counts textually; reality was 473/3087).

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

docs/INTEGRATION.md

@@ -17,6 +17,23 @@ how those two halves meet.
 
 ---
 
+## 0.  Three ways to integrate — pick your tier
+
+This guide covers the **embedded C++** path. Since the daemon track
+landed there are two higher-level options that need no C++ at all:
+
+| Tier | You write | Best for |
+|---|---|---|
+| **Python client** ([clients/python](../clients/python)) | ~25 lines of Python against `secs_gemd` | new tools, lab/R&D, fastest start |
+| **gRPC, any language** ([proto/secsgem/v1](../proto/secsgem/v1/equipment.proto)) | a thin client in Go/C#/Java/… | existing controllers, multi-process tools |
+| **Embedded C++** (this guide) | a main() over `gem::EquipmentRuntime` | in-process integration, custom transports |
+
+In the daemon tiers `secs_gemd` owns the durable HSMS link — your tool
+software can crash/upgrade/restart without the fab host noticing. See
+[DAEMON_ROADMAP.md](DAEMON_ROADMAP.md) for status.
+
+---
+
 ## 1.  What you get vs. what you build
 
 ```