histdb: add connectioninfo.md with verified Runtime DB access

Captures the working SQL Server connection state on this machine:
server (localhost / MSSQLSERVER), database (Runtime), Windows-auth
account (DESKTOP-6JL3KKO\dohertj2, sysadmin), the sqlcmd recipe, four
paste-and-run sanity probes including an end-to-end INSQL retrieval,
linked-server roles (INSQL, INSQLD), and alternate client paths
(SSMS / PowerShell / ODBC / pyodbc).

Linked from histdb/README.md Layout and Resource index per
DOCS-GUIDE.md. Mirrors the pattern grdb/connectioninfo.md uses for
its own DB.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

histdb/README.md

@@ -20,6 +20,7 @@ Read-only reference. There's no code here — these files exist so an LLM can an
 ```text
 histdb/
   README.md                this file
+  connectioninfo.md        Verified Runtime DB connection on this machine (server, sqlcmd recipe, sanity probes)
   01-overview.md           OLE DB provider, linked server, extension tables, four-part / OPENQUERY / OPENROWSET
   02-syntax-limits.md      Supported / unsupported SQL features, joins, sub-SELECTs, time-domain extensions overview
   03-retrieval-modes.md    Every wwRetrievalMode value (Cyclic, Delta, Full, Interpolated, BestFit, Average, Min, Max, Integral, Slope, Counter, ValueState, RoundTrip, Predictive, BoundingValue)
@@ -33,6 +34,7 @@ histdb/
 
 | Task | Go to |
 | --- | --- |
+| Connect from this machine — server, instance, `sqlcmd` recipe, sanity probes | [`connectioninfo.md`](connectioninfo.md) |
 | Connect to Historian via SQL Server, pick a query style (four-part / view / OPENQUERY / OPENROWSET) | [`01-overview.md`](01-overview.md) |
 | What SQL syntax works and what doesn't (LIKE, IN, OR, joins, CONVERT, sub-SELECTs) | [`02-syntax-limits.md`](02-syntax-limits.md) |
 | Pick the right retrieval mode for the question being asked | [`03-retrieval-modes.md`](03-retrieval-modes.md) |