feat: add Split.io connector

[andrei-hasna]

Summary

• Add first-class connectors/split-io/ package with Split.io Admin API v2 bearer client
• CLI covers workspaces, environments, traffic types, splits, segments, tags, metrics, change requests, attributes, groups, and users
• Register split-io in Developer Tools category near LaunchDarkly

Test plan

• cd connectors/split-io && bun test (7 pass)
• cd connectors/split-io && bun run typecheck
• bun run typecheck (monorepo)
• bun run build
• bun test (1193/1194 pass; 1 pre-existing unrelated failure in CLI > events > lists shared events and webhooks from an isolated store)
• Grep new tree for secrets/internal refs (clean)

[andrei-hasna]

OpenLoops worker update for task 91f60444-5873-4abb-b52f-de39e6522e9c.

I pushed fix commit dbd89b8 to this PR branch. It fixes two Split.io Admin API contract issues found during review:

• change-request approve/decline now use the documented status update endpoint (PUT /changeRequests/{id} with form-encoded status/comment) instead of non-documented approve/decline subpaths.
• segment key upload now uses the documented PUT /segments/{environment}/{segment}/uploadKeys?replace=false endpoint.

Validation:

• bun test connectors/split-io/src/api/client.test.ts: 10 pass, 0 fail.
• bun run typecheck: pass.
• bun run build: pass.
• HOME=/tmp/open-connectors-test-home ... bun test: 1197 pass, 0 fail.
• git show --check --format= HEAD: pass.
• commit diff secret-pattern scan: no matches.
• GitHub CI build: SUCCESS on dbd89b8.

Merge blocker: current GitHub login is andrei-hasna, matching the PR author. reviewDecision is empty and latestReviews is empty, so this worker did not approve or merge. Selected non-author reviewer from routing evidence is kriptoburak; GitHub review request via gh pr edit --add-reviewer kriptoburak failed with a GitHub CLI GraphQL projectCards deprecation error, and the direct requestReviews mutation returned successfully but left reviewRequests empty.