Escaping, table layout, and document fixes

Quoted Klammertext specials (^@ ^| ^# ^^ ^: ^*) and ^'...'^ regions now
survive re-processing (held as escape markers until final output);
:after_apply phase functions receive and return raw target text.

Tables: :hpos element position (center|left|right|<length>) replaces the
unimplemented :center/:indent; the ranged cell override is renamed
:justify; :column_width works in html (colgroup widths) and gains
'fill' -- the remaining width, capped at the column's widest entry, in
both targets; a table wider than the text column warns on the console;
table edges without an outer line set their text flush on the margins.

@document: no empty title bar for untitled documents; @vfill fills to
the bottom of the window in html (pure CSS); @vspace in plain text;
new @dot klammer; monospace email links.

sks/table/css/table.css

@@ -21,11 +21,18 @@ td {
     vertical-align: middle;
 }
 
-/*
-td:first-child {
+/* Edge cells of a table with no outer vertical line (classes emitted by
+   table.py): the outer padding is dropped so the cell text aligns with
+   the text margin.  With an outer line the padding stays -- text against
+   a border looks worse than text inset from a margin.  The tex
+   counterpart is @{} in the column spec. */
+.Fl {
     padding-left: 0;
 }
-*/
+
+.Fr {
+    padding-right: 0;
+}
 .line_top {
     border-top: 1px black solid;
 }
@@ -75,6 +82,21 @@ td:first-child {
     text-align: right;
 }
 
+/* A cell of a 'fit' column mixed with sized columns: nowrap floors the
+   column at its widest entry (the tex \widthof semantics).  In a
+   full-width table (fractions/'*') the Wpct 1% width is added -- the
+   classic shrink idiom, so the column survives surplus distribution and
+   the extra window width flows to the sized columns.  In a content-sized
+   'fill' table Wpct must NOT be used: a percentage cell blows an
+   auto-width table up to full width. */
+.Wfit {
+    white-space: nowrap;
+}
+
+.Wpct {
+    width: 1%;
+}
+
 .cell_arrow {
     padding: 1rem;
     font-size: 1.5rem;