docs(milestone): complete v1.9 — verify + review + audit + tag v1.9.0

---ci---
project: acdl
phase: 0
milestone: v1.9
status: complete
requirements:
  covered: [REQ-100, REQ-101, REQ-102, REQ-103, REQ-104, REQ-105, REQ-106, REQ-107, REQ-108, REQ-109, REQ-110, REQ-111]
  partial: []
---/ci---

v1.9 milestone COMPLETE. All 12 requirements satisfied.

Verify: 4 layers PASS (structural 26/26 files, behavioral 493 tests +
run_ci.sh + run_platform.sh --check-only green, security, quality).
Review: 0 P0, 0 P1 (READY TO SHIP). REVIEW.md reconstructed (D-086).
Audit: PASS (reconstruction, file discipline, branch hygiene, commit
discipline — 12/12 commits with ---ci--- blocks).

Updated:
- .ciagent/REQUIREMENTS.md: v1.9 section marked complete; traceability
  table REQ-100..111 added.
- .ciagent/ROADMAP.md: v1.9 marked complete; Phase 43 added.
- .ciagent/PROJECT.md: v1.9 objective marked complete.
- .ciagent/config.json: milestone v1.9 status -> complete.
- .ciagent/REVIEW.md: reconstructed with v1.9 content (D-086).
- .ciagent/VERIFY.md: v1.9 4-layer verify.
- .ciagent/AUDIT.md: v1.9 audit (PASS).
- uses:/ref: bumped @v1.6 -> @v1.9 in contracts/, deploy workflows,
  docs/consumer-guide.md (D-071 successor).

Tag v1.9.0 created next; floating v1.9 + v1 tags updated.

.github/workflows/deploy.yml

@@ -8,8 +8,8 @@
 # declared difference is the forge/runtime, not the stages or commands.
 #
 # Consumer repos invoke this workflow via a versioned tag (floating MAJOR + MINOR):
-#   uses: acdl/.gitea/workflows/deploy.yml@v1.6   (Gitea)
-#   uses: acdl/.github/workflows/deploy.yml@v1.6  (GitHub)
+#   uses: acdl/.gitea/workflows/deploy.yml@v1.9   (Gitea)
+#   uses: acdl/.github/workflows/deploy.yml@v1.9  (GitHub)
 #
 # Unversioned references (@main, bare) are discouraged — the consumer's setup
 # must be immutable + resilient. The versioned tag is the only immutability
@@ -82,7 +82,7 @@ jobs:
         with:
           repository: acdl/acdl
           path: platform
-          ref: v1.6
+          ref: v1.9
 
       - uses: actions/setup-python@v5
         with: