fix(deparser): keep the constraint name on EXCLUDE constraints

[pyramation]

Summary

Constraint() only emitted CONSTRAINT <name> for a whitelist of contypes, and CONSTR_EXCLUSION was missing — so a named exclusion constraint silently lost its name on deparse:

-- in
CONSTRAINT one_pending_per_database EXCLUDE USING btree (database_id WITH =) WHERE (status = 'pending')
-- out (before)
EXCLUDE USING btree (database_id WITH =) WHERE (status = 'pending')

That's a real semantic loss: the constraint gets an auto-generated name, so ALTER TABLE ... DROP CONSTRAINT one_pending_per_database and migration diffs break. Found while chasing the ⚠️ AST round-trip diff detected! warning during pgpm package in constructive-db (metaschema_public.database_transfer).

-if (node.conname && (… || node.contype === 'CONSTR_NOTNULL')) {
+if (node.conname && (… || node.contype === 'CONSTR_NOTNULL' || node.contype === 'CONSTR_EXCLUSION')) {

Fixture added to __fixtures__/kitchen-sink/misc/issues.sql (inline named EXCLUDE + ALTER TABLE ADD CONSTRAINT ... EXCLUDE USING gist), regenerated via npm run kitchen-sink. Full deparser suite passes (295 suites / 715 tests).

Link to Devin session: https://app.devin.ai/sessions/5cfcc6690b574cdd96de080ee3b94b4e
Requested by: @pyramation

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