Run sqlc fmt across all 800 PostgreSQL/MySQL endtoend configs and verify
each result three ways: regenerate and compare code with embedded SQL
stripped (AST-based), and for MySQL compare canonical parse trees of the
original and formatted queries with identifier case preserved.

21 configs need fixes, reducing to six root causes: PostgreSQL prints
@name params as '@ name' (dropping them from codegen); the dolphin
printer folds identifier case, corrupts literals (NULL -> '', 1.0 -> 0),
drops DISTINCT / UNION ORDER BY / GROUP_CONCAT ORDER BY / optimizer
hints / UPDATE JOIN ON clauses and SET qualifiers, loses DDL type
attributes, and prints SHOW WARNINGS as its internal SELECT form.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UZBvADuHMZEjoF551NccgP

Fix the six root causes found by running sqlc fmt across the endtoend
corpus (see fmt-verify/README.md):

PostgreSQL: a named parameter with a cast (@name::type) printed as
'@ name::type' because the cast binds tighter than the @ operator, so the
printer saw a prefix operator and added a space — silently dropping the
parameter from generated code. Prefix sigils now glue to operands that
start with an identifier.

MySQL (dolphin): the formatter reprinted from the compiler's normalized
AST, which loses information the compiler doesn't need but a formatter
must keep. sqlc fmt now uses a format parser that preserves identifier
case (table names are case-sensitive on most servers), and the converter
keeps what it used to drop:

- NULL, TRUE/FALSE, and decimal literals convert by datum kind, so
  NULL no longer prints as '', 1.0 as 0, or true as 1. This also fixes
  type inference: a bool literal column is now bool, not int32
  (selectstatic golden regenerated).
- SELECT DISTINCT keeps its DISTINCT.
- The ORDER BY of a compound (UNION) statement survives.
- GROUP_CONCAT(... ORDER BY ...) keeps its ordering.
- Optimizer hints (/*+ ... */) are carried through to printing.
- Multi-table UPDATE keeps its JOIN's ON condition and the table
  qualifiers in SET.
- DECIMAL(p,s) precision and UNSIGNED survive in column definitions.

Backstop: dolphin now implements Fingerprint (via marino's restore with
identifier case preserved and redundant parens unwrapped), giving MySQL
the same proof PostgreSQL has: fmt accepts a formatted statement only
when it provably means what the author wrote, and otherwise leaves the
statement exactly as written. That is what fixes SHOW WARNINGS, which
the parser rewrites into a synthetic SELECT for analysis: it now falls
back to the original text instead of printing the internal form.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UZBvADuHMZEjoF551NccgP

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UZBvADuHMZEjoF551NccgP