Pre-existing: naive `?` → `$n` rewrite in postgres connectors, and missing optional peer deps

[pi0x]

Two pre-existing issues surfaced while reviewing the Neon connector in #191. Both were deliberately left out of that PR because fixing them touches connectors the PR doesn't own.

1. normalizeParams rewrites ? that aren't placeholders

The ? → $n rewrite is a naive global regex, so it also rewrites ? inside string literals and the jsonb key-existence operators (?, ?|, ?&):

const normalizeParams = (sql) => { let i = 0; return sql.replace(/\?/g, () => `$${++i}`); };

normalizeParams("SELECT * FROM t WHERE data ? 'key' AND id = ?");
// → SELECT * FROM t WHERE data $1 'key' AND id = $2

normalizeParams("SELECT * FROM t WHERE note = 'why?' AND id = ?");
// → SELECT * FROM t WHERE note = 'why$1' AND id = $2

In both cases the operator/literal is corrupted and the placeholder numbering desyncs from the bound parameters, so the real placeholder becomes $2 while only one param is passed.

Any query using the jsonb ? family, or a literal containing ? (a URL with a query string, a question mark in text), hits this.

The same function is duplicated in three connectors:

• src/connectors/postgresql.ts:49
• src/connectors/pglite.ts:50
• src/connectors/cloudflare-hyperdrive-postgresql.ts:60

A fixed version — a scanner that skips single/double-quoted spans, -- and /* */ comments, and ?| / ?& / ?? — landed in src/connectors/_internal/neon.ts as part of #191 (with unit tests). The three above could adopt it; sharing one implementation from _internal/ seems better than a fourth copy.

2. pg and @planetscale/database are not optional peer dependencies

AGENTS.md states the project value as "Zero runtime deps — all backend drivers are optional peer dependencies", but pg (used by the postgresql connector) and @planetscale/database are declared only as devDependencies, with no peerDependencies / peerDependenciesMeta entry:

peerDependencies: @electric-sql/pglite, @libsql/client, better-sqlite3,
                  drizzle-orm, kysely, mysql2, sqlite3

So installing db0 and importing db0/connectors/postgresql gives no peer-dependency signal that pg is required. #191 adds @neondatabase/serverless and neon-new as optional peers; these two would make the set consistent.

Unrelated and lower priority, but noticed nearby: exports["./connectors/*"].types points at ./dist/connectors/*.d.ts, while obuild emits *.d.mts — there are no .d.ts files in dist/connectors/.

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_{🤖 This issue was drafted by Claude (Opus 4.8) via Claude Code during review of #191. The repros above were executed, not inferred, but a human should sanity-check the proposed direction before anyone acts on it.}