feat: add User-Agent header to all HTTP requests (DIS-41)

[ckorhonen]

Add User-Agent header to all HTTP requests

Summary

Adds a User-Agent: opensea-cli/<version> header to every HTTP request made by OpenSeaClient, enabling server-side traffic segmentation by channel (CLI vs MCP vs other consumers) in Datadog/analytics.

• Version is injected at build time via tsup's define option (__VERSION__), avoiding any runtime dependency on file-system layout
• Both tsup.config.ts and vitest.config.ts read package.json and define __VERSION__ so the constant is available in builds and tests
• A private defaultHeaders getter centralizes the shared header set (Accept, User-Agent, x-api-key), used by both get() and post()
• Test assertions use expect.objectContaining with a strictly-anchored regex (/^opensea-cli\/\d+\.\d+\.\d+$/) to validate the header value

Confidence: 🟢 High — small, well-scoped change. Lint, type-check, and all 151 tests pass locally.

Updates since last revision

Addressed review feedback from @ckorhonen:

1. Build-time version injection — replaced createRequire/require("../package.json") with tsup define: { __VERSION__: JSON.stringify(pkg.version) }. Eliminates the CJS require() call in an ESM-only codebase and removes runtime dependency on dist/ ↔ package.json relative path.
2. Anchored test regex — added $ to regex end (/^opensea-cli\/\d+\.\d+\.\d+$/) to reject malformed values like opensea-cli/1.2.3-garbage.
3. Extracted defaultHeaders getter — private getter on OpenSeaClient removes header duplication between get() and post().

Review & Testing Checklist for Human

• Verify __VERSION__ is correctly inlined after build: run npm run build && grep 'opensea-cli/' dist/index.js — should show the literal version string (e.g. opensea-cli/0.4.1), not __VERSION__
• Confirm the post() spread ({ ...this.defaultHeaders }) correctly includes Content-Type when a body is provided — the test covers this but worth a quick manual check of the logic

Notes

• Test assertions use expect.objectContaining instead of exact header matching to accommodate the new header without breaking if header order changes. This is marginally less strict than before.
• The $-anchored regex means pre-release versions (e.g. 1.2.3-beta.1) would fail the test assertion — this is intentional per reviewer preference for strict semver matching.
• Linear ticket: DIS-41
• Devin Session
• Requested by: @ckorhonen

---

[devin-ai-integration]

Original prompt from Chris K

Please work on ticket "[Tracking] Add User-Agent header to opensea-cli" ([DIS-41](https://linear.app/opensea/issue/DIS-41/tracking-add-user-agent-header-to-opensea-cli))

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

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[ckorhonen]

Code Review

Overall: Approve with suggestions — All 151 tests pass. Clean, well-scoped change.

Suggestions

1. Replace createRequire with build-time version injection. The createRequire(import.meta.url) + require("../package.json") pattern works, but introduces a synchronous CJS require() in an ESM-only codebase and depends on file-system layout. Recommend using tsup's define option instead:

   // tsup.config.ts
   define: { __VERSION__: JSON.stringify(pkg.version) }
   
   // client.ts
   declare const __VERSION__: string
   const USER_AGENT = `opensea-cli/${__VERSION__}`

   This eliminates the runtime dependency on file layout and is zero-cost (inlined at build time).

2. Test regex should anchor the end — /^opensea-cli\/\d+\.\d+\.\d+/ should be /^opensea-cli\/\d+\.\d+\.\d+$/ to prevent matching malformed values like opensea-cli/1.2.3-garbage.

3. Minor: Header duplication — Both get() and post() now have identical header sets. Consider extracting a private defaultHeaders getter for maintainability.

I've pushed a commit with fixes 1 and 2.