[connector] Add Linear connector

[sabbah13]

Linear is one of the most-requested issue trackers. The cursor primitive is updatedAt + node id.

API: https://developers.linear.app/docs/graphql/working-with-the-graphql-api
Filter: { updatedAt: { gt: cursor }, assignee: { isMe: { eq: true } } } so we only pull issues assigned to the user.

Files to create:

• packages/connector-issues-linear/src/index.ts
• packages/connector-issues-linear/src/auth.ts (Linear API key)
• packages/connector-issues-linear/test/contract.test.ts

Owner-first rule: only push items where assignee is the user. Don't include creator-only or watcher items - those become noise.

Estimated effort: ~50 lines + 1 contract test. Reference: packages/connector-email-gmail/.

[sabbah13]

Closing as already supported via Cowork's native MCP infrastructure (entry linear in packages/plugin/.mcp.json).

To use Linear with Cowork Tasks: open Customize → Connectors in Cowork, find Linear, click Connect. Then run /cowork-tasks:triage-now.

Cowork Tasks does not maintain custom connector packages - it composes Cowork's hosted MCP servers, which handle auth, polling, and rate limiting upstream. See the new policy in CONTRIBUTING.md (landing in #38).