100%/F: S10F5/F6 multi-line + honest 100% in COMPLIANCE.md + README pass

The final additions: S10F5/F6 multi-line terminal display (closes the
last partial Additional capability — Equipment Terminal Services flips
✅), and a thorough COMPLIANCE.md / README pass that states the 100%
claim honestly.

Catalog + handlers

  data/messages.yaml         S10F5 / S10F6 added.
  apps/secs_server.cpp       router.on(10, 5) iterates the line list,
                             acks with S10F6.
  tests/test_messages.cpp    Round-trips a 3-line multi-line display.

COMPLIANCE.md  (rewritten)

  Every GEM Fundamental ✅.  Every GEM Additional that E30 binds to a
  concrete message set ✅.  New §7 "Explicitly out of scope (with
  reasons)" calls out E40 Material Movement (separate SEMI standard),
  multi-block SECS-I (HSMS-irrelevant), HSMS-GS (HSMS-SS covers all
  modern equipment), Equipment Processing States (tool-specific by
  spec; engine provided), persistent on-disk spool (quality of
  implementation), E42 Enhanced PP (separate standard), S10F7 broadcast
  (rarely used), JIS-8/C2 (not used in Western fabs).

  New §8 "What '100% GEM-compliant' honestly means here" — this is a
  GEM-conformant *runtime stack*, not a GEM-conformant *tool*.
  Marketing a tool as GEM-compliant additionally needs (1) running a
  GEM RTS against the tool, and (2) per-vendor application wiring
  between the generic stores and the real sensors / recipe engine /
  alarm sources.

README.md  (rewritten)

  Architecture diagram updated to reflect the actual store list (nine
  stores).  "Adding a capability" section gives four worked examples
  — new SVID, new host command with side effects, new state
  transition, new SECS-II message — none of which requires a C++
  change.  Demo walkthrough updated to reflect the current 20-step
  flow including the S1F19/F20 self-report, S1F21/F22 DVID discovery,
  and the spool window.

Code clarity
  include/secsgem/gem/data_model.hpp  Composite-doc comment updated
  to say "every GEM data category" rather than the stale "seven
  focused stores".

Verified
  - Tests: 84 cases / 487 assertions pass.
  - Demo: 198 server/host log lines; exits 0 end-to-end.

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

data/messages.yaml

@@ -888,3 +888,24 @@ messages:
     function: 4
     builder: s10f4_terminal_display_ack
     body: {kind: scalar, item_type: BINARY_BYTE, enum: TerminalAck, param: ack}
+
+  # S10F5 / S10F6 — Terminal Display, Multi-line (host -> equipment).
+  - id: S10F5
+    stream: 10
+    function: 5
+    w: true
+    builder: s10f5_terminal_display_multi
+    parser: parse_s10f5
+    body:
+      kind: list
+      struct_name: TerminalDisplayMulti
+      fields:
+        - {name: tid, shape: {kind: scalar, item_type: BINARY_BYTE}}
+        - name: lines
+          shape: {kind: list_of, element: {kind: scalar, item_type: ASCII}}
+
+  - id: S10F6
+    stream: 10
+    function: 6
+    builder: s10f6_terminal_display_multi_ack
+    body: {kind: scalar, item_type: BINARY_BYTE, enum: TerminalAck, param: ack}