chore: publish hygiene — LICENSE, package metadata, drop src from tarball

[AlejandroFabianCampos]

Summary

Three pre-publish hygiene fixes flagged in the v0.2.0 review:

1. Add LICENSE — package.json declares MIT but the file was missing. Standard MIT, copyright Quiknode Inc., 2026.
2. Add package.json metadata — repository, homepage, bugs, engines.node (≥22). Without these, npm and GitHub presentation are degraded and the documented Node-22 requirement isn't enforced.
3. files field aligned with the MPP first-party SDK spec — ["dist", "src", "!src/**/*.test.ts", "!src/__tests__"]. The spec recommends shipping src so consumers get "Go to Source Definition" in editors (matches mppx, tempo, ecosystem convention). Tests are excluded via gitignore-style negation in the files array — no .npmignore needed.

Test plan

• npm run verify (lint + typecheck + 82 tests pass, 9 skipped)
• npm pack --dry-run — 91 files, 46.9 kB
  • dist/ + src/ source included
  • 0 test files (*.test.ts, src/__tests__/) leak into tarball
  • LICENSE and README.md auto-included
  • Declaration maps in dist/ now resolve correctly (sources are present)

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