docs(overview): the EDIT limits truncate, and the viewer default is 2000 not 500

Review 431: dc-overview.md still said "Up to 500 rows can be edited (in the web
editor) at one time" - the wrong number (DC_MAXOBS_WEBEDIT ships at 250) and, once
dc/dc#352 lands, the wrong behaviour (an over-limit selection is served truncated
with a warning, not refused or capped at a count). It now names both limits,
whichever binds first, and links to the options that set them.

Sweeping for the same stale figure turned up dcu-tableviewer.md, which says 500
twice and uses 500 in its worked example of the row count above the grid.
DC_MAXOBS_WEBVIEW has been 2000 since 20261003_row_and_cell_limits.sas (the
migration records 500 -> 2000), and mpe_makedata seeds 2000, so those three
places were two releases out of date. Fixed here, and flagged in the PR reply as
VIEW rather than EDIT in case it belongs in its own change.

Checked: no "500 rows" or stale abort wording left in docs/, and the two anchors
the overview now links to (dc_maxobs_webedit, dc_maxcells_webedit) exist on the
published options page.

docs/dc-overview.md

@@ -35,7 +35,9 @@ When importing an excel file, all rows are loaded into the web page.  You have a
 A CSV upload bypasses the part where the records are loaded into the web page, and ALL rows are sent to the staging area directly.  This makes it suitable for larger uploads.
 
 ## Edit Stage Approve Workflow
-Up to 500 rows can be edited (in the web editor) at one time.  These edits are submitted to a staging area.  After one or more approvals (acceptances) the changes are applied to the source table.
+The EDIT screen loads up to [DC_MAXOBS_WEBEDIT](/dcc-options/#dc_maxobs_webedit) rows (250 by default), or as many rows as fit within [DC_MAXCELLS_WEBEDIT](/dcc-options/#dc_maxcells_webedit) (200,000 cells) - whichever is reached first, so a wide table loads fewer rows than a narrow one.  A larger table is not refused: it loads truncated, with a warning against the table name, and the filter is the way to reach the rest.
+
+These edits are submitted to a staging area.  After one or more approvals (acceptances) the changes are applied to the source table.
 
 ![screenshot](img/dcu_flow.png)