feat(format): add the commaStyle and logicalOperatorPlacement options

[edjubert]

What

Two new formatter options, both defaulting to the current behaviour:

Option	Default	Values
commaStyle	"trailing"	"trailing", "leading"
logicalOperatorPlacement	"trailing"	"trailing", "leading"

They control where the separator sits when a list or a condition breaks across lines.
A list that fits on one line is unaffected.

commaStyle=leading

select
	staging.buildings.identification_number
	, staging.buildings.construction_year
	, staging.buildings.address_fk
from
	staging.buildings;

logicalOperatorPlacement=leading

where
	staging.buildings.construction_year > 1950
	and staging.buildings.address_fk is not null
	and staging.buildings.identification_number is not null;

with trailing (today's output, unchanged) the same condition ends each line with and.

Why

Leading commas are a long-standing convention in analytics/ETL SQL: a line can be commented out or reordered without touching its neighbours, and a missing or extra comma is visible in a diff.
The same argument applies to AND/OR in long WHERE clauses.
Both are pure style preferences, hence options rather than a change of default.

Implementation

The separator is chosen at emission time, not at render time: node_list.rs emits the comma before or after the line break depending on commaStyle, and bool_expr.rs does the same for the boolean operator.
That is why the emitter needs access to the configuration (see the prerequisite PR).

Wiring: pgls_configuration (serde + bpaf CLI flags --comma-style / --logical-operator-placement), pgls_workspace settings, docs/features/formatting.md, and docs/schema.json.

Tests

Two new fixtures with snapshots at width 80, plus the full existing snapshot suite unchanged (the defaults preserve today's output).

The two preparatory commits

The first two commits of this PR are shared, byte for byte, with the three other formatter-option PRs open alongside it:

• #796 — clauseBodyStyle / isolateSemicolon
• #797 — layout
• #798 — castStyle

The shared commits are:

• test(pretty-print): allow per-fixture format configuration
• refactor(pretty-print): thread the format config into the emitter

They are carried in each PR so every option remains independently reviewable and mergeable.
Whichever PR lands first, I will rebase the other three to remove the duplicate commits.

Merge them in whatever order suits you; nothing here depends on the others.