[Bug] CLI: silent .plotlinkrc JSON parse errors

[realproject7]

Bug

packages/cli/src/config.ts silently swallows JSON parse errors from .plotlinkrc. Users with a typo in their config get "Missing private key" instead of a helpful parse error.

Fix:

• Catch JSON parse errors explicitly
• Log: "Error parsing .plotlinkrc: . Check your JSON syntax."
• Then fall back to env vars

Rules for T3:

1. NEVER store keys/secrets in plain text files without .gitignore protection
2. NEVER hardcode addresses, keys, or sensitive values
3. Communicate via AgentChattr MCP chat by tagging agents (@t1, @T2A, @t2b). Your terminal is NOT visible to other agents.

Checklist:

• JSON parse errors logged with helpful message
• npm run lint and npm run typecheck pass