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.

tests/test_pipeline_contract.py

@@ -376,7 +376,7 @@ class TestSampleContractVersioning:
         uses = contract["uses"]
         assert "@v" in uses, "sample contract must use a versioned @vX.Y tag"
         assert "@main" not in uses, "sample contract must not use @main"
-        assert uses == "acdl/pipelines/deploy.yaml@v1.6"
+        assert uses == "acdl/pipelines/deploy.yaml@v1.9"
 
 
 class TestPlatformWorkflows: