feat(workspace): chat-first auth workspace boot

[hachej]

Summary

• adds chat submit interception/draft restore seams for child-app chat-first auth flows
• renders authenticated workspace chat after identity match while tree/session/runtime warmup runs in the background
• adds workbench-local readiness overlay and structured WORKSPACE_NOT_READY tool/readiness handling
• adds focused unit/e2e coverage and docs for the unified chat-first workspace boot contract

Reviews

• Gemini/Claude reviewer passes during implementation; final moved branch contains the reviewed implementation.

Validation

Previously run in the original main worktree before moving this implementation into .worktrees/chat-first-auth-workspace-boot:

• pnpm --filter @hachej/boring-core test src/app/front/tests/CoreWorkspaceAgentFront.test.tsx
• pnpm --filter @hachej/boring-workspace test src/app/front/tests/WorkspaceBackgroundBoot.test.tsx src/app/front/tests/WorkspaceAgentFront.test.tsx src/app/front/tests/WorkspaceBootGate.test.tsx
• pnpm --filter @hachej/boring-agent test src/server/catalog/tests/mergeTools.test.ts src/server/tests/registerAgentRoutes.test.ts src/front/tests/toolRenderers.test.tsx src/front/tests/ChatPanel.test.tsx src/front/pi/tests/piChatProjection.test.ts
• pnpm --filter @hachej/boring-core run typecheck
• pnpm --filter @hachej/boring-workspace run typecheck

Note: rerunning tests from the new worktree currently needs dependencies installed in that worktree; pnpm reported missing node_modules there.