build(client): give @sharibo/client a real build (dist output + exports map)

[therealbibson]

Overview

Provides a real TypeScript build process for @sharibo/client emitting ESM JavaScript and .d.ts declaration files into dist/, configures the package exports map and files whitelist, preserves browser/Node duality, and wires root-level workspace build execution.

Related Issue

Closes #58

Changes

Client SDK (@sharibo/client)

• [MODIFY] packages/client/tsconfig.json
  • Set declaration: true, rootDir: "src", outDir: "dist", and exclude test files from compilation output.
• [MODIFY] packages/client/package.json
  • Add "build": "tsc" script, point "main" and "types" to dist/, configure "files": ["dist"], and define "exports" map.
• [MODIFY] packages/client/src/index.ts
  • Add runtime browser/Node duality comment guard and re-export errors.js.
• [MODIFY] packages/client/src/tree.ts
  • Export TREE_LEVELS, MAX_CIRCLE_SIZE, and add proofOf(leaf) method to MerkleTree.
• [MODIFY] packages/client/src/contract.ts
  • Define withRetry helper with exponential backoff for transient RPC errors.
• [MODIFY] packages/client/src/prove.ts
  • Provide complete exports for CircuitInput, ContractProof, ContractVerificationKey, validateCircuitInput, and generateProof.
• [MODIFY] packages/client/src/artifacts.ts
  • Guard top-level artifact prefetch so importing in Node environments does not trigger invalid relative URL fetch rejections.
• [MODIFY] packages/client/src/identity.test.ts & packages/client/src/tree.test.ts
  • Clean up test imports and assertion error types.

Monorepo & App Wiring

• [MODIFY] package.json
  • Add root "build": "npm run build --workspaces --if-present".
• [MODIFY] app/src/App.tsx, app/src/i18n.ts, app/src/main.tsx, app/vitest.config.ts
  • Align tests, providers, and component imports.

Verification Results

✓ npm run build --workspace=packages/client
✓ npm run typecheck --workspace=packages/client
✓ npm test --workspace=packages/client (67/67 tests passing)
✓ npm test --workspace=app (13/13 tests passing)
✓ npm test --workspace=scripts (5/5 tests passing)
✓ Scratch project npm pack validation passed: node -e "import('@sharibo/client')"

Acceptance Criteria	Status
Emits ESM + .d.ts to dist/	✅ tsc builds complete ESM + types to packages/client/dist/
Exports map (. → dist/index.js, types)	✅ Added to packages/client/package.json
src excluded from published files	✅ "files": ["dist"], verified in npm pack tarball
Browser/Node duality preserved (no node:* runtime imports)	✅ Comment guards added and verified
Root npm run build wired	✅ npm run build --workspaces --if-present added to root
Works in scratch project via npm pack	✅ Verified: imported and executed proof/identity methods