Add Initiative workspaces and proposal provenance

[Cyber-preacher]

What

• add Initiative list, creation, workspace, board, threads, chat, members, and settings surfaces
• add Initiative proposal attribution and visible Initiative provenance across proposal and feed views
• add reusable Initiative API, UI helpers, form controls, routes, navigation, and tests
• use Proposal ready as the board state for work prepared for proposal creation

Why

Active human nodes need a persistent collaborative workspace before work becomes a formal Vortex proposal. Initiative administrators also need an explicit, immutable way to publish proposals under an Initiative identity.

Validation

• yarn test (32 files, 135 tests)
• yarn typecheck
• yarn prettier:check
• yarn build
• git diff --check

Temporary preview data and the local .codex directory are excluded.