feat(sub-accounts): pass vaultAddress on exchange mutations + trading banner

[vipineth]

Parent PRD

#75

What to build

When a sub-account is active, every exchange mutation (place order, cancel order, update leverage, switch margin mode, etc.) must pass the sub-account address as vaultAddress so Hyperliquid routes execution to the correct account. Without this, orders placed while a sub-account is selected would incorrectly land on the master account.

In addition, add a persistent banner at the top of the trading terminal when a sub-account is active: "Trading on behalf of sub-account: [name]" with a button to switch back to master. Disable the deposit and external withdrawal buttons (with an explanatory tooltip) since Hyperliquid only supports L1 deposits to the master account.

Acceptance criteria

• Placing an order while a sub-account is active sends vaultAddress: <subAccountAddress> in the request
• Cancelling an order while a sub-account is active includes vaultAddress
• Updating leverage or margin mode while a sub-account is active includes vaultAddress
• A banner is visible in the trading terminal whenever a sub-account is the active account
• The banner shows the sub-account name and includes a "Switch to Master" control
• Clicking "Switch to Master" in the banner resets the active account to master and hides the banner
• Deposit button is disabled with a tooltip when a sub-account is active
• External withdrawal is disabled with a tooltip when a sub-account is active

Blocked by

• Blocked by feat(sub-accounts): wire all data hooks to active account #76 (data hooks must use active address before mutations do)

User stories addressed

• User story 12 (persistent banner when sub-account active)
• User story 13 (trading actions execute in the active account's context)
• User story 14 (deposit and withdrawal disabled for sub-accounts)

[vipineth]

Closing as wontfix. Sub-account switching was reverted in 990bff4 — the store, hook, and user-menu wiring no longer exist. This issue's spec assumes those modules. If sub-accounts return, we'll file fresh issues against the current codebase.