feat(credential-sharing): end-to-end-encrypted team credential sharing

Adds a `team` credential provider + team/member management so teammates can
share secrets by email instead of passing .env files over chat. Fully E2E:
the server only ever stores ciphertext, per-member sealed vault keys, and
public keys — it never sees a plaintext value or the vault DEK.

Plugin (@logicsrc/plugin-credential-sharing)
- crypto.ts: X25519 identity keys, per-vault DEK (secretbox), DEK sealed to
  each member's pubkey (crypto_box_seal), value encrypt/decrypt (libsodium)
- identity.ts: local ~/.logicsrc/identity.json (0600) holding the device key
  + API token; never uploads the secret key
- client.ts: typed /api/credshare client
- providers/team.ts: `team:<slug>/<vault>` CredentialProvider (inspect,
  readValues=decrypt, write=encrypt, rollback); fingerprints match env so
  env<->team diffs line up
- fixes latent libsodium-wrappers ESM load bug (createRequire) here + in
  github-secrets

Server (commandboard-api /api/credshare)
- zero-knowledge router: email-code auth, keys, teams, members, invites,
  vaults, sealed grants, ciphertext secrets, audit; membership authz in app
- CredShareStore abstraction: in-memory (dev/tests) + Supabase (prod)
- Resend email transport for login codes + invites (no-op -> echoes locally)
- supabase migration: credshare_* tables, deny-by-default RLS

CLI
- real `logicsrc login` (email code -> token + key upload)
- `logicsrc teams create/list/invite/accept/members/vaults/grant/push/pull`

Web (logicsrc.com/teams + /teams/accept)
- management surface only (browser holds no private key, never decrypts):
  login, view teams/members/vaults, invite, accept

Tests: crypto round-trip, server contract (invite->accept->push->grant->pull
+ authz boundaries), and a real HTTP+client+crypto E2E asserting the server
never holds plaintext. Full workspace build + tests green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.env.example

@@ -33,3 +33,15 @@ SH1PT_WEBHOOK_SECRET=
 # webhook authenticates callers by this secret instead). Generate with:
 #   openssl rand -hex 32
 BLOG_WEBHOOK_SECRET=
+
+# --- Team credential sharing (commandboard-api /api/credshare) ---
+# Production storage. Without these, the API uses an in-memory store (dev/tests).
+SUPABASE_URL=
+SUPABASE_SERVICE_ROLE_KEY=
+# Email transport for login codes + team invites. Without RESEND_API_KEY the API
+# returns codes/tokens in its responses (local dev only — never in production).
+RESEND_API_KEY=
+CREDSHARE_EMAIL_FROM=LogicSRC <noreply@logicsrc.com>
+LOGICSRC_WEB_URL=https://logicsrc.com
+# Web page → API base (public). Falls back to https://commandboard.run.
+NEXT_PUBLIC_COMMANDBOARD_API_URL=