#81 build: enforce Cloudflare Pages 20k-file / 25 MiB limits

What

The build can emit artifacts Cloudflare Pages rejects:

• 25 MiB per file: a 64 MB repo blob was written to raw/big.bin silently.
• 20,000 files per deployment: raw/ + files/ + dir pages scale with repo size; no count check.
• repo.bundle / repo.tar.gz can exceed 25 MiB on larger histories.

Reproduced

dd if=/dev/zero of=big.bin bs=1M count=64
hu13 build /tmp/bigprobe -o /tmp/bigout
find /tmp/bigout -type f -size +25M   # raw/big.bin 64 MB

No warning; Pages would fail the deploy with a generic error.

Impact

The advertised Pages Free target fails late and opaquely for ordinary asset-heavy repos. The current repo fits (1,325 files), but nothing enforces it.

Fix

• Add a Pages budget check (always-on or --pages): every output file ≤25 MiB, output file count ≤20,000; report the offending paths and suggest Git LFS / external assets.
• Include bundle/tarball sizes.
• Tests for a >25 MiB fixture and for the file-count boundary (can use a small threshold under cfg(test) or a --max-file-bytes override).
• Mention the limits in the deploy wiki.