refactor(admin): extract parsePropsParam helper for props query param

[JonasJesus42]

Replaces the nested try/catch props-decoding in src/admin/render.ts with a flat, reusable parsePropsParam helper (src/admin/propsParam.ts) that tries each encoding strategy — plain encodeURIComponent(JSON) and base64 btoa(encodeURIComponent(JSON)) — in order and returns null on total failure, so render.ts now logs a warning instead of silently rendering with {}. The helper also adds a typeof === "object" guard that rejects valid-JSON-but-not-object inputs. The invoke.ts GET branch now reuses the same helper, unifying both admin endpoints and adding the previously-missing base64 fallback to /deco/invoke. Verified with npm run typecheck and npm run build.

🤖 Generated with Claude Code

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Summary by cubic

Extracted a reusable props parser for admin query params that unifies decoding in render and invoke, adds base64 support to /deco/invoke, and only accepts plain object props.

• Refactors
  • Added parsePropsParam in src/admin/propsParam.ts that tries URI-encoded JSON then base64(URI-encoded JSON), uses an internal tryOrNull, returns null on failure, and accepts only plain objects (rejects arrays/primitives).
  • Updated render.ts to use the helper and warn on parse failure instead of defaulting to {}.
  • Updated invoke.ts GET branch to reuse the helper and gain the base64 fallback.

^{Written for commit 5411dd2. Summary will update on new commits.}