Invalidate stale bboxes in coordinate mutators

[khalilurrrahmanridoykhan]

What changed

• removes cached bbox values recursively after flip, toMercator, toWgs84, and truncate change coordinates
• preserves the existing clone-versus-mutate behavior
• adds regression coverage for both default cloning and mutate: true
• updates the truncate fixture that previously retained an invalid bbox

Why

These functions change coordinate positions but retained cached bounding boxes describing the pre-mutation geometry. A later bbox lookup could therefore return stale coordinates. This follows the behavior established in #3106 and reuses the recursive removeBbox helper introduced there.

Validation

• pnpm --filter @turf/flip test — 9 passed
• pnpm --filter @turf/projection test — 52 passed
• pnpm --filter @turf/truncate test — 17 passed
• TypeScript checks for all three packages
• Prettier check on all changed sources/tests/fixture
• ESLint on all changed TypeScript files
• git diff --check
• repository pre-commit hook