refactor: three copies of quote-aware SQL scanning, and plugin-pull's paren-stripper has already diverged

[alvarogar4]

Description

Peeling redundant parentheses off a SQL expression is now implemented twice, and scanning a SQL string while ignoring quoted regions is implemented three times. The copies have already drifted apart, and each drift is a real bug (#195, #196).

Location	What it does	Tracks quotes?
packages/core/src/key-clause.ts — splitTopLevelComma	split on top-level commas	' " `
packages/core/src/projection.ts — stripWrappingParens	peel wrapping parens	' " `
packages/plugin-pull/src/index.ts:396 — normalizeWrappedTuple	peel wrapping parens	none
packages/clickhouse/src/create-table-parser.ts — extractCreateTableBody	find the column-list body	' " only (#196)

normalizeWrappedTuple and stripWrappingParens are the same algorithm — same guard (startsWith('(') && endsWith(')')), same depth walk, same "only strip when the leading paren closes at the very end" rule — but they now behave differently:

• stripWrappingParens is quote-aware and peels every redundant layer (PR fix(pull): capture index-only projections and render them correctly #193 — peeling only one layer was non-idempotent and made every generate re-emit a drop + rebuild).
• normalizeWrappedTuple is neither. It peels a single layer and miscounts parens inside quoted identifiers.

So (`weird)name`) normalizes correctly in core and incorrectly in plugin-pull, and ((a, b)) peels fully in core but not in pull.

Why it wasn't folded into #193

normalizeWrappedTuple backs splitTopLevelCommaSeparated, which parses key clauses (primaryKey / orderBy) — not projections. Changing it touches the same code path implicated in #194 and #190, so it was deliberately left alone to keep that PR scoped to the reported bug.

Proposed Fix

Export one quote-aware scanning primitive from @chkit/core and have all four call sites use it:

• splitTopLevelComma (already exported) stays as-is.
• Export stripWrappingParens (or a peelRedundantParens) and delete normalizeWrappedTuple in favour of it.
• Rework extractCreateTableBody to use the shared quote handling (bug: create-table parser does not track backtick identifiers, silently dropping projections on tables with parens in a column name #196).

Sequencing note: fixing normalizeWrappedTuple changes how primaryKey/orderBy are parsed on pull, so it is best done alongside #194/#190 with their tests in place, rather than as a standalone refactor.

Verification

• The paren/quote behavior table above becomes a single shared unit test rather than one per copy.
• packages/plugin-pull key-clause parsing is unchanged for the cases it already handles — assert against existing pull tests before and after.
• No behavior change to projections (covered by packages/core/src/index.test.ts).

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Found while verifying #183 / PR #193. Related: #194, #195, #196.