fix: normalize INTO clause whitespace + add OUT parameter test fixtures

[pyramation]

Summary

This PR adds test fixtures for OUT parameters with SELECT INTO multiple variables, and fixes a pretty-printing bug where the INTO clause insertion left weird whitespace.

Test Fixtures Added:

• Test 15: OUT parameters with SELECT INTO multiple variables (auth function pattern with 6 OUT params)
• Test 16: OUT parameters with SELECT INTO STRICT

Bug Fix - Whitespace Normalization:
When PostgreSQL parses SELECT ... INTO var FROM ..., it strips the INTO var but leaves the original whitespace behind. This caused weird formatting like:

SELECT x INTO y                                         FROM z

The fix normalizes whitespace after INTO insertion:

• If original had newlines → use newline + 4-space indent
• If original was just spaces/tabs → collapse to single space

Updates since last revision

• Added packages/plpgsql-deparser/AGENTS.md documenting the complete workflow for adding test fixtures
• Updated generated.json with the new fixtures (now 192 fixtures total)
• Added explicit snapshot tests in deparser-fixes.test.ts for the OUT parameters pattern (2 new snapshots)
• Fixed whitespace normalization in deparseExecSql() - this updates several existing snapshots where FROM clauses now have consistent indentation

Review & Testing Checklist for Human

• Review the whitespace normalization fix in plpgsql-deparser.ts (lines ~1488-1504) - verify the 4-space indent is appropriate and won't break existing consumers
• Inspect updated snapshots in hydrate-demo.test.ts.snap, schema-rename-mapped.test.ts.snap, and plpgsql-pretty.test.ts.snap - these show the formatting change impact on existing tests
• Verify the deparsed output in new snapshots has correct INTO id, user_id, access_token... ordering matching SELECT columns
• Run cd packages/plpgsql-deparser && pnpm test to confirm all 62 tests pass (192 fixtures round-trip)

Recommended test plan: Parse and deparse a PL/pgSQL function with a long SELECT INTO clause, verify the FROM clause appears on a new line with reasonable indentation rather than excessive spacing.

Notes

This PR is part of a larger effort to support OUT parameters in constructive-db's auth functions. The TypeScript deparser already handles PLpgSQL_row.fields for the (unnamed row) case - these fixtures ensure that pattern continues to work correctly.

Link to Devin run: https://app.devin.ai/sessions/f47b5a7894fa44548bb2fa47a647e0c3
Requested by: Dan Lynch (@pyramation)

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