Sprint 18 ceremony

[laynepenney]

Summary

Sprint 18 ceremony PR: sprint-18 -> main

• feat: interactive web dashboard with codex support, drag-drop upload, textarea, key palette, ANSI rendering (feat: interactive web dashboard with codex support #677)
• fix: suppress channel join/leave spam in dashboard and reaper (feat: interactive web dashboard with codex support #677)
• fix: SQLite lock contention in channel reap path (fix: SQLite lock contention in channel reap path #672)
• feat: channel seam hooks for premium coordination gating (feat: channel seam hooks for premium coordination gating (#553) #668)
• test: OSS protocol definitions for org + entitlements seam (test: make channel worktree tests self-contained #670)
• test: make channel worktree tests self-contained

Test plan

• 1978 tests passed, 0 failed (excluding benchmark fixture tests)
• All channel tests (261) pass
• Dashboard tested manually in browser

Premium boundary: recall is OSS (channel infrastructure, dashboard, test coverage)

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[laynepenney]

Closing in favor of v2 ceremony PR (rebase approach to avoid merge commits)