fix: v3.5.1 — classic lightened to ░ for distinct style cycling

[aedneth]

Summary

classic/bold have shared block's exact 5-row × 4-col silhouette since v3.5.0, differing only by shade (classic ▒, bold ▓). Both sit visually close to solid block █, so cycling d through the three solid styles showed no observable difference — reported while dogfooding in a minimized window.

This lightens classic's fill from ▒ to ░ (U+2591 light shade) so the three solid styles read as three distinct surfaces at the same locked footprint:

style	fill	look
block	█	full / solid
classic	░	light / airy
bold	▓	dark / dense

At a 5-row × 4-col cell there is only one readable solid digit shape, so the distinction between solid styles must come from fill texture (distinct shapes like the old 9-row fonts are geometrically impossible without breaking the footprint parity that was the original requirement). ░/█/▓ is the widest three-way split. bold and block are unchanged; footprint parity, scaling, and small-window rendering are identical to v3.5.0 — texture-only refinement.

Note: the related "classic/bold fall back to block in a minimized window" report was a stale process — a long-running session executing the pre-v3.5.0 build; the v3.5.0 on-disk build already fixed the load/fallback path. This PR addresses the remaining visual-distinctiveness half.

Verification

• Empirical: footprint+ink parity (classic ░ / bold ▓ / block █ are byte-identical silhouettes) and a no-fallback sweep across a 70–100 × 13–22 window grid both pass.
• Gate: typecheck ✓ · lint ✓ · build ✓ · 604 tests ✓.

🤖 Generated with Claude Code