Add opt-in options for a compact multiline formatting style

[sw1sh]

Summary

Adds seven opt-in options that together produce a compact, consistent multiline
style (one element per line, never a mid-expression wrap), best used with
BreakLinesMethod -> "LineBreakerV2". All seven default to the current
behavior, so existing output and the test suite are unchanged.

These came out of formatting a real paclet to a house style that the existing
options could not express.

Options

• "KeepBindingsInline" — decide whether a scoping (Module/Block/With/
  Function) or control (If/Switch/Which/...) construct must explode based
  on the width of its leading line (head + binding list / condition, e.g.
  Block[{a, b},) rather than the maximum width of the whole construct. A long
  body line no longer forces a short binding list / condition onto its own line.

• "SpaceAfterControlOpener" — insert a space after the opener of a multiline
  control structure so the condition lines up with the branches (If[ cond,).

• "GlueAssignmentRHS" — keep the RHS of an assignment (Set, SetDelayed,
  UpSet, ...) on the operator line (f := Block[{) instead of breaking after
  the operator. Applies to top-level and inner assignments.

• "TrailingCommas" — when breaking a comma-separated sequence whose elements
  are all single-line, keep the comma at the end of the element line; when an
  element is multiline, the comma stays on its own line as a boundary marker.

• "InlineShortControl" — a control structure that fits within LineWidth
  and whose branches are all single-line stays on one line (If[a, b, c])
  instead of always breaking.

• "SpaceAfterPrefixNot" — insert a space after a prefix Not (! cond).

• "SpaceAroundPatternOperators" — space Pattern (:), Optional (:),
  and PatternTest (?) like ordinary operators (name : pat, x_ ? NumericQ);
  MessageName (::) and Power (^) stay tight.

Example (all options on, LineWidth -> 60):

run[dir_String] := Block[{cmd, res},
    If[ ! FileExistsQ[dir],
        Return[<|"code" -> 1, "err" -> "missing"|>]
    ];
    res = exec[cmd];
    res
]

Tests

Adds Tests/GuideStyle.mt (12 tests) covering each option and a combined case.
The existing suite is unchanged (the new options default off).

Notes

Implementation is localized to the scoping/control indenters, the prefix and
operator/comma renderers, and the pattern-operator spacing rule in Indent.wl,
plus option plumbing in CodeFormatter.wl. Each option is gated, so default
formatter output is unchanged.

🤖 Generated with Claude Code