v1.2.1 — the cloudcost CLI actually starts now

Fixed

• The cloudcost CLI could not start. dist/cli.js shipped with two
  #!/usr/bin/env node lines — one from src/cli.ts and one from the
  banner.js that tsup.config.ts injects into every bundle. Node strips only
  a line-1 shebang, so the second parsed as code and the binary died with
  SyntaxError: Invalid or unexpected token. The shebang is now declared in
  exactly one place (the tsup banner). This affected every published release up
  to and including 1.2.0, so 1.2.0's --currency flag was unreachable in
  practice. The MCP server entrypoint (cloudcost-mcp) was never affected —
  src/index.ts carried no shebang of its own.

Tests

• test/unit/cli/shebang.test.ts guards the artifact users actually run: no
  source entrypoint may declare a shebang, each built bin must contain exactly
  one on line 1, and dist/cli.js must start under Node. The existing CLI
  suites all execute src/cli.ts through the TypeScript loader, which is why a
  build-output defect went unnoticed across six releases.