docs(pdftract-1lw3): add verification note for release cascade workflow

Documents the completed implementation of pdftract-release-cascade
WorkflowTemplate and pdftract-tag-trigger Argo Events Sensor.

Acceptance criteria:
- PASS: All infrastructure files committed in declarative-config
- WARN: Runtime verification deferred (kubectl not available in env)

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

notes/pdftract-1lw3.md

@@ -0,0 +1,78 @@
+# pdftract-1lw3 Verification Note
+
+## Bead: Argo WorkflowTemplate: pdftract-release-cascade (orchestrate all per-channel templates from a tag)
+
+Date: 2026-05-20
+Commit: b06a448d65861c4de7005d7c3b9a274098656e76
+
+## Summary
+
+Implemented the top-level pdftract-release-cascade WorkflowTemplate that orchestrates all per-channel publish templates in correct dependency order. Also created the Argo Events sensor that automatically triggers the cascade on milestone tag pushes.
+
+## Files Created/Modified
+
+### jedarden/declarative-config
+
+1. k8s/iad-ci/argo-workflows/pdftract-release-cascade.yaml (442 lines)
+   - DAG topology with correct dependency ordering
+   - parallelism: 10 for wide fan-out to SDK templates
+   - continueOn: failed for failure isolation
+   - Re-runnable via argo retry
+   - Release summary exit handler with per-channel status reporting
+   - SDK publish templates as placeholders (when: false) for Phase 8
+
+2. k8s/iad-ci/argo-events/pdftract-tag-trigger.yaml (139 lines)
+   - Argo Events Sensor for Forgejo webhook integration
+   - Filters for v*.*.* milestone tag pushes only
+   - Extracts tag, version, commit-sha from webhook payload
+   - Triggers cascade with correct parameters
+
+3. k8s/iad-ci/argo-events/forgejo-eventsource.yml (+4 lines)
+   - Added pdftract webhook entry on port 12000, endpoint /pdftract
+
+4. k8s/iad-ci/argo-events/webhook-ingressroute.yml (+6 lines)
+   - Added Traefik route for /pdftract path on webhooks-ci.ardenone.com
+
+## Acceptance Criteria Status
+
+### PASS
+- [PASS] WorkflowTemplate file lands at correct path in jedarden/declarative-config
+- [PASS] The Argo Events Sensor lands at correct path in jedarden/declarative-config
+- [PASS] The Sensor is wired to the pdftract repo's tag-push events via forgejo-eventsource and webhook-ingressroute
+- [PASS] DAG topology correctly encodes dependencies
+- [PASS] Failure isolation implemented via continueOn: failed at per-channel task level
+- [PASS] Parallelism set to 10 to avoid cluster starvation
+- [PASS] SDK templates are placeholders (when: false) for Phase 8 implementation
+- [PASS] Release summary exit handler reports per-channel status
+- [PASS] Manual launch instructions documented in sensor comments
+- [PASS] ADR-009 compliance: cascade orchestration is purely on iad-ci cluster
+
+### WARN
+- [WARN] Test cascade submission against a fresh tag could not be verified (kubectl not available)
+- [WARN] Simulated failure of pdftract-py-ci could not be tested (kubectl not available)
+- [WARN] Cascade re-run behavior could not be verified (kubectl not available)
+- [WARN] Slack/Discord notification is implemented as console output; actual webhook integration would require additional ExternalSecret
+
+## DAG Topology
+
+pdftract-build-binaries (root)
+  ├── pdftract-py-ci (Python wheels to PyPI)
+  ├── pdftract-crates-publish (Rust crates to crates.io)
+  │   └── pdftract-docs-build (mdBook to Cloudflare Pages)
+  ├── pdftract-docker-build (multi-arch images to GHCR)
+  ├── pdftract-sdk-node-publish (npm - Phase 8, when: false)
+  ├── pdftract-sdk-go-publish (go module - Phase 8, when: false)
+  ├── pdftract-sdk-java-publish (Maven Central - Phase 8, when: false)
+  ├── pdftract-sdk-dotnet-publish (NuGet - Phase 8, when: false)
+  ├── pdftract-sdk-ruby-publish (RubyGems - Phase 8, when: false)
+  ├── pdftract-sdk-php-publish (Packagist - Phase 8, when: false)
+  ├── pdftract-sdk-swift-publish (SPM - Phase 8, when: false)
+  └── pdftract-github-release (joins on all above)
+
+## Webhook URL
+https://webhooks-ci.ardenone.com/pdftract
+
+## References
+- Plan section: Release Engineering / Argo WorkflowTemplates, line 3382
+- Plan section: Release Engineering Acceptance Criteria, lines 3439-3448
+- ADR-009: Argo-only CI/CD