[Bug] Portfolio excludes authenticated Robinhood connection despite working account reads

What happens

On Vibe-Trading 0.1.15 on macOS (Apple Silicon), Robinhood OAuth succeeds and direct account and position reads succeed when an account is supplied. However, Portfolio → Manage accounts offers no Robinhood connection.

Reproduction

1. Authenticate the built-in robinhood-live-mcp connector.
2. Verify account and position reads with the selected account.
3. Open Portfolio → Manage accounts → Open connection center.
4. Robinhood is unavailable for portfolio selection.

Code evidence

agent/src/trading/connections.py: is_portfolio_connection_profile requires profile.readonly to be true. agent/src/trading/connectors/robinhood/profiles.py: the only Robinhood profile declares account.read and positions.read, but readonly=False.

Expected behavior

Provide a read-only Portfolio view of an authenticated Robinhood account, or clearly explain the unsupported connection. Preserve the existing separation between portfolio reads and order execution. A dedicated read-only profile may be more appropriate than relaxing the gate. Account selection also needs to be carried through to the read calls.

No account identifiers, balances, tokens, or private logs are included.