fix(cli): production-grade peer disambiguation (alpha.42)

Three bugs compounding when multiple peers share a display name:

1. list_peers (MCP + CLI) truncated pubkey to 12 hex chars with an
   ellipsis. A truncated pubkey cannot be used as a routing key, so
   the caller had no way to disambiguate visually.

2. send_message required the full 64-hex pubkey and refused prefix
   input, forcing callers to rely on --json output to get a full key.

3. Name-based resolution returned the first exact match without
   filtering the caller's own session — so "send to <my-own-name>"
   would bounce against the broker's self-send guard when another
   session of the same user was the intended target.

Fixes:
- list_peers now prints 16-char pubkey prefix labelled "pubkey: …"
  (MCP) and appends it to CLI output
- send_message accepts any 8–64 hex-char prefix and resolves against
  live peer lists across joined meshes; unique match routes, multi-
  match returns a disambiguation error listing each candidate's
  displayName + pubkey + cwd
- Name matches now skip the caller's own session pubkey; multiple
  same-named matches fail loudly with a copy-pasteable pubkey
  disambiguation hint instead of silently picking one
- Full 64-char pubkeys without a live match still queue at the
  broker (preserves offline-delivery semantics)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/cli/src/commands/peers.ts

@@ -61,7 +61,8 @@ export async function runPeers(flags: PeersFlags): Promise<void> {
           if (p.model) meta.push(p.model);
           const metaStr = meta.length ? dim(` (${meta.join(", ")})`) : "";
           const summary = p.summary ? dim(`  — ${p.summary}`) : "";
-          render.info(`${statusDot} ${name}${groups}${metaStr}${summary}`);
+          const pubkeyTag = dim(` · ${p.pubkey.slice(0, 16)}…`);
+          render.info(`${statusDot} ${name}${groups}${metaStr}${pubkeyTag}${summary}`);
           if (p.cwd) render.info(dim(`   cwd: ${p.cwd}`));
         }
       });