chore: prepare CHANGELOG for v3.10.0 release

[richardwooding]

Splits ## [Unreleased] into ## [3.10.0] - 2026-09-09. No code changes.

What's in v3.10.0

PR
#192	feat: WithPlaceholderStyle — render ? for callers whose driver rebinds placeholders (GORM, sqlx.Rebind, squirrel)
#193	fix: has() detects JSON columns from the schema, not a hardcoded name list
#194	fix: comprehension JSON access derives from the range, not variable names

Together, #193 and #194 remove the last hardcoded column- and variable-name lists from the converter, completing the sweep started in #62 (#61, #59):

$ grep -rn '\[\]string{"' --include='*.go' . | grep -v _test | grep -v /examples/
$

Minor, not major

Two BREAKING behaviour notes are recorded under ### Changed, but both stay within /v3 per the skill's rule — the same call made for #113, whose heuristic removal was BREAKING with a niche blast radius. Neither changes an exported signature:

• has() on a JSON column now requires the column to be declared via WithSchemas or WithJSONVariables.
• Field access on a comprehension variable follows the schema rather than the variable's name.

Callers already passing schemas are unaffected; those with JSON columns outside the old seven names get correct SQL for the first time.

🤖 Generated with Claude Code