fix(cli): decrypt falls back to member secret key when session key fails

When Alice's session-A encrypts a direct message to Bob (target = Bob's
stable member pubkey) and Bob's session-B receives it, Bob has BOTH an
ephemeral session secret key and the member secret key. The old code
only tried session_sk, then silently failed with '⚠ message from
<sender> failed to decrypt' even though the message was valid —
just encrypted to the member key.

Now: try session first, fall back to member on null. Matches the
sender side's choice freedom (encrypt using either key).

Repros when: user opens multiple Claude Code sessions (all use the
same member key but each generates its own session key), and one
session sends to another by display-name resolution which returns
the member pubkey.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/cli/package.json

@@ -1,6 +1,6 @@
 {
   "name": "claudemesh-cli",
-  "version": "1.0.0-alpha.33",
+  "version": "1.0.0-alpha.34",
   "description": "Peer mesh for Claude Code sessions — CLI + MCP server.",
   "keywords": [
     "claude-code",