chore(release): 0.1.3 — remove unused @openauthjs/openauth (removes 14 hono vulns)

The package had zero references anywhere in src/, tests, docs, or config —
only listed in package.json as a leftover from the original upstream
implementation. esbuild was already tree-shaking it out, so the published
plugin bundle (SHA f6a56195...) is byte-for-byte identical to 0.1.2.

Security impact: bun audit 27 -> 7 vulnerabilities. All 14 hono CVEs eliminated
plus 6 other openauth-transitive vulns. Remaining 7 are dev-only toolchain
issues (vitest/vite/picomatch/yaml/brace-expansion) waiting on upstream.