Add `-Compact` support to Format-Toml (and/or ConvertTo-Toml) for inline table/dotted-key collapsing

[MariusStorhaug]

Request

Format-Toml (added in #20) currently only expands structure into [a.b] header form and offers -Indent to control cosmetic whitespace around that expanded form. There's no way to go the other direction: collapsing structure into TOML's compact forms.

TOML supports several compact representations that are semantically equivalent to the expanded [a.b] header form:

• Inline tables: point = { x = 1, y = 2 } instead of a [point] section (single-line only, per spec).
• Dotted keys: physical.color = "orange" instead of a full [physical] table with a color key.
• Arrays of inline tables: points = [{ x = 1, y = 2 }, { x = 3, y = 4 }] instead of repeated [[points]] sections.

A -Compact switch (or similar) on Format-Toml would collapse eligible tables into these forms, giving users a "canonical compact form" the same way -Indent gives a "canonical expanded form".

Desired capability

Format-Toml -InputObject $s -Compact
# [server]
# host = "localhost"
# port = 8080
#
# becomes:
# server = { host = "localhost", port = 8080 }

Technical decisions to make

• This is not a text-level post-process like -Indent/Add-TomlIndentation — collapsing requires restructuring the serialization itself, most likely in ConvertTo-TomlTableObject / Add-TomlTableText (or a parallel emission path), since it changes which TOML construct is emitted for a given value, not just its surrounding whitespace.
• Array-of-tables ([[x]]) sections don't have as clean a mapping to a single-line inline-table array once nesting or dotted-key children are involved — needs a defined collapsing rule (e.g. only collapse array-of-tables into inline-table arrays when every table is "leaf" — no further nested tables).
• TOML forbids multi-line inline tables, so collapsing arbitrarily deep/wide tables can produce very long single lines. May need a size/depth cutoff, or leave that entirely to the caller (no automatic fallback to expanded form).
• Decide whether this lives as ConvertTo-Toml -Compact (so Import-Toml | ConvertTo-Toml -Compact also benefits) with Format-Toml -Compact simply passing it through, or as Format-Toml-only logic. Placing it in ConvertTo-Toml seems more consistent with the module's reuse-first design (Format-Toml is currently just ConvertFrom-Toml | ConvertTo-Toml plus indentation).

Acceptance criteria

• -Compact produces valid, parseable TOML equivalent in meaning to the expanded input.
• Round-trip: ConvertFrom-Toml (Format-Toml $s -Compact) equals ConvertFrom-Toml $s in data terms.
• Clear documentation of which structures are/aren't collapsed and why (esp. array-of-tables edge cases).

Related

• Add Format-Toml function for normalization #3 — Format-Toml normalization (this issue's -Compact is a natural follow-up, discussed during PR 🚀 [Minor]: Format-Toml normalizes TOML to canonical form #20 review).