fix(text): add automatic glyph texture padding

[han4wluc]

Summary

• add automatic text texture padding based on font size so overhanging glyphs are not clipped without caller-provided textStyle.padding
• keep explicit padding and shadow padding supported by using the largest required texture reserve
• update the Mr De Haviland D/L VT specs to verify the default user path without explicit padding
• bump package version to 1.23.6

Testing

• bunx vitest run spec/util/toPixiTextStyle.spec.js spec/elements/textHoverLayout.spec.js
• bun run vt:generate
• bun run vt:report (703/703, 0 mismatches)
• bunx prettier --check src spec/util/toPixiTextStyle.spec.js spec/elements/textHoverLayout.spec.js vt/specs/textbasic/mr-de-haviland-correct-d-l-overhang.yaml vt/specs/textbasic/mr-de-haviland-leading-l-overhang.yaml package.json
• bunx vitest run (83 files, 585 tests)
• pre-push hook: bunx prettier --check src
• pre-push hook: vitest run (83 files, 585 tests)