demo: reconstruct sales demos for an accounting audience

Replaces the Shopify / RevOps / Bookkeeper demo trio with three accounting
personas that share one buyer, each entering through a workflow where a
messy export costs money — all running the same saved 4-step pipeline:

- bank_reconciliation.csv (Bookkeeper): 26 -> 20 rows, 6 double-posted
  transactions caught after date+amount standardization.
- vendor_1099.csv (AP / 1099): 24 records -> 8 vendors, 7 missing EINs
  recovered via dedup merge — the 1099-complete story.
- ar_open_invoices.csv (AR): 26 -> 21 rows, 5 double-entered invoices
  removed, blank status backfilled from the twin row.

Every number is validated against the live engine and pinned by
tests/test_demo_pipelines.py (read path mirrors app_demo._load_demo:
dtype=str, keep_default_na=False). Rewires src/gui/app_demo.py PERSONAS
(keys bookkeeper / ap-1099 / ar-aging, accounting H1/sub/CTA) and rewrites
docs/DEMO-PLAN.md sections 3/4/7 with the validated outcomes.

(Repo hygiene forced by a partial-clone gap: finalizes the already-deleted,
unreferenced samples/messy_text.csv whose blob was unrecoverable.)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

samples/demo/vendor_1099.csv

@@ -0,0 +1,25 @@
+Vendor,Contact,Email,Phone,EIN,Address,Total_Paid
+Acme Realty,Bob Stein,acme.ap@acmerealty.com,(212) 555-0100,12-3456789,(blank),"$12,400.00"
+acme realty llc,Bob Stein, ACME.AP@AcmeRealty.com ,,—,"118 Canal St, New York, NY 10013","$8,250"
+ACME REALTY,R. Stein,Acme.AP@acmerealty.com,212.555.0100,N/A,TBD,"1,999.99"
+Bright Books Bookkeeping,Dana Cole,hello@brightbooks.com,,98-7654321,(blank),"$6,000.00"
+bright books,Dana Cole,HELLO@brightbooks.com,(415) 555-0142,unknown,"50 Market St, San Francisco, CA 94105","$6,000"
+"Bright Books, LLC",D. Cole, hello@BrightBooks.com,4155550142,98-7654321,unknown,"5,500.00"
+Northwind Logistics,Sam Reyes,ap@northwindlog.com,(312) 555-0198,—,(blank),"$22,750.00"
+northwind logistics inc,Sam Reyes,AP@NorthwindLog.com,,45-6789012,"900 W Loop, Chicago, IL 60607","$22,750"
+Pearl Design Studio,“Jo” Marsh,billing@pearldesign.co,,33-2211000,(blank),"$3,200.00"
+pearl design,Jo Marsh,Billing@PearlDesign.co,(206) 555-0167,TBD,"77 Pike St, Seattle, WA 98101","$3,200"
+PEARL DESIGN STUDIO,J. Marsh, billing@pearldesign.co ,206.555.0167,33-2211000,unknown,"2,800.00"
+Cooper Plumbing,Lee Cooper,office@cooperplumb.com,(617) 555-0133,—,(blank),"$1,450.00"
+cooper plumbing co,Lee Cooper,OFFICE@cooperplumb.com,,TBD,"12 Beacon St, Boston, MA 02108","$1,450"
+COOPER PLUMBING,L. Cooper, office@CooperPlumb.com,6175550133,N/A,unknown,900.00
+Vertex Marketing,Pat Nguyen,accounts@vertexmktg.com,(404) 555-0119,77-8899001,(blank),"$15,000.00"
+vertex marketing group,Pat Nguyen,ACCOUNTS@VertexMktg.com,,unknown,"300 Peachtree St, Atlanta, GA 30308","$15,000"
+Summit Consulting,Ray Brooks,invoices@summitconsult.net,,21-0099887,(blank),"$9,800.00"
+summit consulting llc,Ray Brooks,INVOICES@summitconsult.net,(303) 555-0175,—,"1100 17th St, Denver, CO 80202","$9,800"
+SUMMIT CONSULTING,R. Brooks, invoices@SummitConsult.net ,303.555.0175,21-0099887,TBD,"7,250.00"
+Garcia Catering,Mia Garcia,ap@garciacatering.com,(305) 555-0188,—,(blank),"$4,600.00"
+garcia catering services,Mia Garcia,AP@GarciaCatering.com,,66-1234509,"450 Ocean Dr, Miami, FL 33139",$600.00
+Northwind Logistics,S. Reyes, ap@northwindlog.com ,312.555.0198,45-6789012,TBD,"21,000.00"
+VERTEX MARKETING,P. Nguyen, accounts@vertexmktg.com ,404.555.0119,77-8899001,TBD,"14,500.00"
+GARCIA CATERING,M. Garcia,ap@GARCIACATERING.com,305.555.0188,66-1234509,unknown,"4,200.00"