fix: strip quotes and uppercase EXTRACT field name in deparser

[pyramation]

Summary

The SQL deparser's FuncCall handler for EXTRACT was producing EXTRACT('epoch' FROM x) instead of the correct EXTRACT(EPOCH FROM x). The root cause: the first argument is an A_Const with an sval field, and A_Const deparsing wraps string values in single quotes via QuoteUtils.formatEString(). The EXTRACT branch then passed this quoted string through verbatim.

The fix strips surrounding single quotes and uppercases the field name before formatting the EXTRACT expression. This matches the behavior fixed in constructive-io/constructive-db#748 for the PL/pgSQL-native deparser.

Adds a kitchen-sink fixture (__fixtures__/kitchen-sink/misc/extract.sql) with 18 EXTRACT keyword variants (EPOCH, YEAR, MONTH, DAY, HOUR, MINUTE, SECOND, CENTURY, MILLENNIUM, DOW, DOY, QUARTER, WEEK, TIMEZONE, TIMEZONE_HOUR, TIMEZONE_MINUTE) using the project's standard fixture-based testing pipeline.

Updates since last revision

• Added AGENTS.md at the repo root with project overview, package listing, setup/build/test instructions, and code conventions.
• Added .agents/skills/testing-fixtures/SKILL.md documenting the full fixture-based testing pipeline (how SQL fixtures → generated.json → kitchen-sink test files, how to add new fixtures, pretty-print test pattern, package scripts reference).
• New: Added .agents/skills/code-generation/SKILL.md documenting the protobuf-based code generation pipeline (build:proto across 4 packages), type inference & narrowed type generation (pgsql-types), keyword list generation (@pgsql/quotes), and version-specific deparser generation.
• New: Expanded the testing-fixtures skill to cover PL/pgSQL fixtures (plpgsql-deparser) and transform package kitchen-sink/test:ast workflows, with per-package script reference tables.
• New: Expanded AGENTS.md with a Skills directory, comprehensive root and per-package script reference tables (organized by category: fixtures, code generation, version management, CLI), and a note about not hand-editing generated files.

Review & Testing Checklist for Human

• Quote-stripping robustness: The fix checks for startsWith("'") && endsWith("'"). Verify this won't misfire on E-prefixed strings (E'...') — shouldn't happen since EXTRACT field names are simple keywords, but worth confirming formatEString never adds the E prefix for plain alpha strings.
• Other COERCE_SQL_SYNTAX functions with same issue: Check whether date_part or any other pg_catalog.* function handled in this block has a similar quoting problem with its string arguments (e.g., TRIM, SUBSTRING, OVERLAY all use different arg patterns so likely fine, but worth a glance).
• Verify round-trip: Run cd packages/deparser && npx jest __tests__/kitchen-sink/misc-extract.test.ts to confirm all 18 EXTRACT variants pass the parse→deparse→reparse AST comparison.
• Review skill and AGENTS.md accuracy: Skim AGENTS.md, .agents/skills/testing-fixtures/SKILL.md, and .agents/skills/code-generation/SKILL.md to confirm that documented commands, directory paths, and workflow descriptions match reality. All three were written from code reading — spot-check a few commands (e.g., npm run build:proto in packages/utils, npm run infer in packages/pgsql-types, npm run keywords in packages/quotes) to verify they work as described.

Notes

• All 291 test suites (711 tests, 424 snapshots) pass with this change
• Tests use the standard fixture pipeline (npm run kitchen-sink) rather than ad-hoc test files — generated.json and the kitchen-sink test file were regenerated from the new fixture SQL
• The code-generation skill documents workflows across utils, traverse, transform, pg-ast, pgsql-types, proto-parser, and quotes packages — all based on reading the actual scripts, not existing documentation (there was none)
• Upstream ref: constructive-io/constructive-db#748

Link to Devin session: https://app.devin.ai/sessions/b02ffea25df94fd0a78385bbe5846415
Requested by: @pyramation

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