feat(desktop): add live organization directory

[ArchieeR]

Summary

• add a live, clickable Organization directory for Buzz-managed agents, teams, and channels
• expose a narrow read-only Tauri projection that excludes keys, prompts, environment data, commands, paths, raw errors, and private messages
• add a versioned portable organization export and owner-selected JSON save flow for strict local consumers without making Buzz depend on external organization policy
• handle disconnected, malformed, and duplicate identity states with focused UI and E2E coverage

Product boundary

This PR keeps native Buzz Organization read-only: it displays a safe projection of Buzz-managed agents, teams, channels, and runtime facts, and does not write departments, reporting lines, assignments, capabilities, grants, or organization policy.

Agent Tower is the canonical harness-agnostic agent manager and organization/governance/capability system. Buzz remains authoritative for public identity, communities, channels, messaging, presence, and its native managed-agent runtime controls, but those local controls are not a canonical cross-runtime desired-policy store. The portable export is a safe compatibility seam for read-only integration without making upstream Buzz depend on Agent Tower.

A later follow-up may make Buzz Organization bidirectional only by calling the same governed Agent Tower control core—with the same validation, revision preconditions, approvals, atomic persistence, invalidation, and receipts. It must not introduce a duplicate Buzz policy store or parallel policy logic.

Messaging teams remain distinct from organization hierarchy.

Safety

The Organization read path:

• uses a public-only managed-agent loader that does not hydrate or migrate OS-keyring secrets
• directly projects an explicit allowlist of safe fields
• does not load personas or process prompts, environment variables, auth tags, executable paths, logs, raw errors, allowlists, or private messages
• exports stable public identities as buzz-agent:<lowercase 64-hex pubkey>
• emits runtime IDs only, never custom commands or executable paths
• writes the organization-sensitive, secret-free snapshot atomically with owner-only permissions on Unix after explicit native destination selection

Verification

• . ./bin/activate-hermit && just ci — passed (exit 0)
• desktop Tauri Rust: 2403 passed, 0 failed, 14 ignored
• mobile Flutter: 1261 passed
• focused Organization/export Rust tests: passed
• Organization Playwright smoke: 5 passed, including cancel/success/error export behavior and screenshot evidence
• desktop checks, TypeScript, formatting, clippy, builds, file-size ratchet, and git diff --check passed

UI screenshots/recording will be added before marking ready for review.