M8: GUI polish, n8n workflow-3 fixes, RAGcore retrieval root-cause and fix

GUI: dashboard Attention Queue presents a curated severity mix instead of pure
severity-sort (grouped Now/Today/Later headers); Today's Movements seed data
curated so a fresh reset shows a credible day (2+ departures, 2+ returns), with
a new seed-integrity test; About Demo restructured into a compact grid with
progressive disclosure for technical sections; Duplicate Merge shows match/conflict
counts, hides matching fields by default, and previews the final merged record
before confirmation.

Repo hygiene: removed a stray empty `backend;C` directory and an untracked 31MB
zip export; `.gitignore` now excludes future archive exports.

n8n: fixed invalid JSON (a missing `},` between two node objects) in the committed
`fleet-ops-vehicle-return.json` -- the file could not be parsed. Live-validated
workflow 3 (RAGcore Procedure Sync): found and fixed a real defect (three body
parameters had a stray trailing `}}`) and a missing Error Workflow wiring, both
via the safe `n8n import:workflow` CLI path; exported the corrected, still-
inactive workflow as the new source of truth and updated MANIFEST.md/check_drift.py.
Publishing it (starts real daily unattended runs) remains a separate decision.

RAGcore: root-caused and fixed (live, approved) the "zero retrieval candidates"
bug -- a filesystem permission bug (`embedding_profiles.json` unreadable by the
app's own runtime user) that broke every retrieval call before it reached Qdrant.
Every other suspect (grants, scope resolution, Qdrant filters, embeddings) was
verified healthy first. Found a second, deeper gap: the reranker adapter calls
an Ollama HTTP route that does not exist on the deployed Ollama version, so
`/v1/answers` still returns `not_answerable`. `KNOWLEDGE_PROVIDER` stays `demo`
until that is resolved on the RAGcore side. Evidence-based MCP Hub integration
status (real tool-call audit history, not just a boolean flag) replaces the old
`configured`/`not_configured` guess. Full findings in
`docs/final-integrations/current-state-audit.md`.

Backend: 172 tests passing, ruff clean, mypy clean (50 files). Frontend: tsc
clean, production build clean.

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

backend/app/api/routers/dashboard.py

@@ -72,8 +72,14 @@ def get_dashboard(
                 issue_ref=issue.public_ref,
             )
         )
-    attention_items.sort(key=lambda item: _SEVERITY_ORDER.get(item.severity, 3))
-    attention_items = attention_items[:8]
+    # Curate a credible severity mix instead of letting `high` dominate every slot:
+    # each item's real severity is unchanged, only the display selection is capped per
+    # tier (a handful of "now", then "today", then "later") so a heavy day of high-severity
+    # issues doesn't crowd out medium/low ones the operator should still see.
+    high_items = [i for i in attention_items if i.severity == "high"]
+    medium_items = [i for i in attention_items if i.severity == "medium"]
+    low_items = [i for i in attention_items if i.severity == "low"]
+    attention_items = (high_items[:3] + medium_items[:3] + low_items[:2])[:8]
 
     today = _today()
     bookings = db.scalars(select(Booking)).all()