Bind GitHub MCP tools to channel repositories

Assistant-model: GPT-6 Sol
Assistant-workflow: harness-stack (run f6f676b9-6506-489b-93e2-2616ea55c6a8)
Assistant-duration: 30m blocked, estimated 60m
Assistant-verification: Bun GitHub unit passed: 21/21 allowlist, binding, errors, cache transitions and race regressions
Assistant-verification: Bun ci passed: mise exec -- bun run ci (dprint, oxlint, tokens)
Assistant-verification: Bun typecheck passed: mise exec -- bun run types (workspaces and E2E)
Assistant-verification: Bun unit passed: mise exec -- bun test (1552 pass, 2 PostgreSQL skips)
Assistant-verification: Playwright E2E passed: mise exec -- bun run e2e --workers=1 (230/230, fresh build)
Assistant-verification: agent-browser Edge manual scenario unavailable: GitHub Next SSO authorization gate yielded Access unavailable, so no Planner reply proven
Assistant-verification: agent-browser recording passed: 44.1s WebM records SSO gate and Access unavailable, not a Planner reply
Assistant-verification: qlty metrics and smells passed: changed harness and bridge sources analyzed
Co-authored-by: Alex Lavaee <lavaman131@github.com>