fix(release): remove dead skipNpm config

[jasonkuhrt]

Summary

• remove the inert skipNpm key from the public release config schema and resolved config shape
• remove the stale README example entry and point operators at release apply --dry-run
• add a regression test that proves the dead config surface is gone

Testing

• bun run --cwd packages/release test packages/release/src/_.test.ts --testNamePattern "does not expose inert skipNpm configuration"
• bun run release:verify

Closes #147

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This change is