feat(skills): add a corbits skill chain

[TheGreatAxios]

Summary

• Add corbits, a hub skill that catalogs the @corbits/* packages, the shared install rules (peer pins, one copy of @intx/*), and how each kind plugs into Interchange.
• Add five reference skills it points to: corbits-inference (OpenAI Responses, Codex, xAI, Ollama, oauth-core, credential-http), corbits-system-one (typed decisions for routing and gating), corbits-tools (MCP, Gmail, Granola), corbits-hub-libs (cron, webhooks, artifacts, memory, mailbox, agent-token, embedding, reranking), and corbits-ui-apps (react-ui, workbench, Solution Builder).
• Background skills only (no slash). Content comes from the corbitsdev repos updated in the last week. Alpha caveats are stated: 0.x APIs, a codex and xai peer-range mismatch with oauth-core 0.3.0, stubbed Granola tools, unreleased subcritical.
• Add the names to the telemetry allowlist and update PRODUCT, TELEMETRY, and the manifest description.

Verification

• bun run check passes (7,870 tests).

Fixes CL-9674

[linear-code]

CL-9674