feat: add reth snapshots viewer app

[emmajam]

Summary

• Add apps/reth-snapshots-viewer to the monorepo with package, TypeScript, Wrangler, and README setup
• Convert the Worker from itty-router to hono to match the Tempo snapshots migration pattern
• Wire production deployment and PR preview deployment for reth-snapshots-viewer
• Add the app to root README and AGENTS app tables
• Carry over the cold-cache R2 indexing optimization used by tempo-snapshots-viewer

Preview Deployment

This follows the Tempo snapshots viewer setup:

• apps/reth-snapshots-viewer/wrangler.json has workers_dev: true and preview_urls: true
• .github/workflows/pull-request.yml includes reth-snapshots-viewer in the single-env preview matrix
• The preview job runs pnpm gen:types, pnpm build, then wrangler versions upload from apps/reth-snapshots-viewer

Validation

• Parsed .github/workflows/main.yml and .github/workflows/pull-request.yml with Ruby YAML loader
• pnpm --filter reth-snapshots-viewer check
• pnpm --filter reth-snapshots-viewer build
• Local wrangler dev smoke tested / and /api/snapshots with 200 responses
• pnpm check
• pnpm check:types
• pnpm precommit

No app-specific pnpm test was run because reth-snapshots-viewer does not define a test script.

[github-actions]

Bundle Size Report

Metric	Size	Δ Change
Total	4.6 MB	+407.2 KB (+9.4%)
Gzip	1.3 MB	+121.2 KB (+9.7%)
Brotli	1.2 MB	+106.0 KB (+9.8%)

Chunk changes (>1KB)

Chunk	Change
assets/chains.js (removed)	-360.7 KB
assets/export-rate-limit.js (removed)	-177.3 KB
assets/wagmi.config.js	-29.5 KB
assets/AbiItem.js (removed)	-27.1 KB
assets/env.js	-9.6 KB
assets/validators.js (removed)	-5.1 KB
assets/call.js	+1.2 KB
assets/_address.js	+1.4 KB
assets/parseAbiItem.js (new)	+1.6 KB
assets/.js	+1.7 KB
assets/known-event-totals.js (new)	+2.0 KB
assets/tempo-queries.js	+2.4 KB
assets/Addresses.js (new)	+9.1 KB
assets/schemas.js	+22.7 KB
assets/structs.js (new)	+23.9 KB
assets/queries.js	+26.4 KB
assets/Connectors.js (new)	+55.5 KB
assets/token.js	+56.1 KB
assets/manifest.js (new)	+173.8 KB
assets/dist.js (new)	+294.0 KB
...and 1 more

Compared against main branch (baseline from 4/27/2026, 4:02:54 PM)

[github-actions]

Cloudflare Deployments

App	Environment	Status	Preview
explorer	devnet	[OK] Deployed	View Preview
explorer	mainnet	[OK] Deployed	View Preview
explorer	testnet	[OK] Deployed	View Preview
fee-payer	devnet	[OK] Deployed	View Preview
fee-payer	moderato	[OK] Deployed	View Preview
fee-payer	privy	[OK] Deployed	View Preview
og	-	[OK] Deployed	View Preview
perf	-	[OK] Deployed	View Preview
reth-snapshots-viewer	-	[OK] Deployed	-
tempo-snapshots-viewer	-	[OK] Deployed	View Preview
tokenlist	-	[OK] Deployed	View Preview

[emmajam]

[emmajam]

Included the upstream Reth changes requested here:

• tempoxyz/reth-snapshots-viewer#21: adds the command / Snapshot URL toggle in the UI, adapted so URL mode displays and copies the manifest URL directly.
• tempoxyz/reth-snapshots-viewer#8: adds explicit X-Cached-At freshness checks, adapted across the full snapshot, API JSON, and rendered HTML caches.

Additional local validation on this update:

• pnpm --filter reth-snapshots-viewer check
• pnpm --filter reth-snapshots-viewer build
• pnpm --filter reth-snapshots-viewer gen:types
• pnpm exec wrangler versions upload --dry-run from apps/reth-snapshots-viewer
• pnpm check
• pnpm check:types
• pnpm precommit
• Local wrangler dev smoke test for / and /api/snapshots