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>

plugins/credential-sharing/src/index.ts

@@ -53,9 +53,44 @@ export {
   dopplerProvider,
   railwayProvider,
   githubSecretsProvider,
+  teamProvider,
   parseEnv,
   applyEnv
 } from "./providers/index.js";
+export {
+  TeamClient,
+  TeamApiError,
+  type TeamClientOptions,
+  type RemoteUser,
+  type RemoteTeam,
+  type RemoteMember,
+  type RemoteVault,
+  type RemoteSecret,
+  type RemoteGrantRow
+} from "./client.js";
+export {
+  generateIdentityKeyPair,
+  generateVaultKey,
+  wrapVaultKey,
+  unwrapVaultKey,
+  encryptValue,
+  decryptValue,
+  publicKeyForSecret,
+  type IdentityKeyPair,
+  type SealedValue
+} from "./crypto.js";
+export {
+  loadOrCreateIdentity,
+  readIdentity,
+  saveIdentity,
+  updateIdentity,
+  requireAuth,
+  verifyIdentityIntegrity,
+  identityPath,
+  logicsrcHome,
+  defaultApiUrl,
+  type LocalIdentity
+} from "./identity.js";
 export {
   createFileCredentialStore,
   createMemoryCredentialStore,