Synth

First maintainer-reviewed pass for SN50 (previously community-seeded/unreviewed, categories empty, no website/source-repo surfaces despite website_url/source_repo already being set). Added the missing website and source-repo surfaces. Fixed 3 surfaces having no probe config at all -- the registry-wide gap tracked in #5932; two of them (leaderboard, validation-scores) reject HEAD (405/404) so their probes use GET. Diffed the full 48-path Swagger 2.0 schema: found the 17 /insights/* GET routes are undocumented-auth-gated in practice despite the schema declaring no security (see gap_notes); the /v2/prediction/*, /rewards/scores, /validation/miner|prompts|realized-path|scores/historical, and /v2/leaderboard/historical|meta-leaderboard/historical routes all require query parameters with no stable canonical value. Added one new no-auth no-param surface: /v2/meta-leaderboard/latest. The on-chain-declared source_repo (github.com/mode-network/synth-subnet) now permanently redirects (301) to github.com/synthdataco/synth-subnet -- same repo, org renamed; updated the tracked source_repo/provider github_url to the current URL since on-chain native_name/description/website_url are otherwise unchanged (not a full identity pivot).