feat(books): update stats to seven books, add opposites and letters

[konjoinfinity]

Summary

This follows up on #243. The stat boxes in the about section of squish.run/books still said the series had 5 books.

• "Books in the series" changes from 5 to 7.
• New box: 12 Pairs of opposites.
• New box: 26 Letters from A to Z. "A to Z" uses non-breaking spaces so the Z doesn't wrap onto its own line on phones.

The stats grid is always two columns, so the six boxes form three even rows at both phone and desktop widths. I checked this locally at 390px and 1280px: no horizontal scroll, and the count-up animation lands on 7, 20, 24, 12, 12, 26.

Type of change

• Bug fix
• New feature
• Performance improvement
• Documentation update
• Refactor / cleanup

Checklist

• pytest tests/ passes locally: not run, this changes static HTML only
• ruff check squish/ tests/ reports no errors: not run, no Python touched
• No hardcoded absolute paths
• No model weights, eval output files, or log files staged for commit
• Changes are scoped to one logical concern
• Performance-sensitive changes include a before/after squish bench run: N/A

Related issues

Follow-up to #243.

🤖 Generated with Claude Code

https://claude.ai/code/session_01R3pogbkBhhhr9h7qHxBWXf

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[konjoinfinity]

G4 · Complexity + Size + DRY is red, but this PR didn't cause it. The step that fails is the 500-line file gate, on squish/backend.py (511 lines, not in .konjo/oversized-allowlist.txt). This PR only changes docs/books/index.html. The Konjo gate fails the same way on main and did so on #243. No fix exists yet: it needs backend.py split or allowlisted, which is outside this PR's scope. I didn't re-run the job because this file-size check gives the same result every time.

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[konjoinfinity]

Test Linux (Python 3.12) is also red, and this PR didn't cause it either. The one failing test is tests/test_wave120_dead_global_purge.py::test_server_line_count_under_threshold: server.py has 6400 lines, ceiling is < 6400. This PR doesn't touch squish/server.py. The file is identical on main, whose CI run after the #243 merge (run 37116529388) also failed. No fix exists yet: it needs server.py trimmed by a line or the ceiling raised, which is outside this PR's scope. The other 6079 tests passed.

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[konjoinfinity]

The other red test jobs (Test Linux (Python 3.11), Test (Python 3.11), Test (Python 3.13)) also fail on code this PR doesn't touch. Linux fails only the server.py line-count test noted above. The macOS jobs add three bfloat16 KV-cache tests that raise ValueError: 'bfloat16' is not a valid PEP 3118 buffer format string:

• test_block_kv_cache_coverage.py::test_to_numpy_f16_bfloat16_fallback
• test_block_kv_cache_coverage.py::test_to_numpy_f32_bfloat16_fallback
• test_prompt_kv_cache_coverage.py::test_to_numpy_mlx_and_bf16_branches

main's CI run after the #243 merge (37116529388) fails the same four tests in the same jobs. This PR only changes docs/books/index.html. No fix exists yet for either issue, and both are outside this PR's scope.

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