test(panel): repair context-client harness and cover submit guards + Enter handling (Closes #555)

[BernardOnuh]

Closes #555.

What

TransactionPanel.test.tsx had 11 pre-existing failures on main — the test if said "All tests pass with npm test", so this PR both repairs the poisoned harness and adds the missing acceptance-criteria coverage.

Harness repair (source of the 11 failures)

• The panel reads client from the useSorokit() context (const { client } = useSorokit()), but every mock in this file only fed getClient() — so a plain object literal had no client key and submitTransaction short-circuited at if (!address || !client) → "Wallet not connected", and no modal-paths could ever complete. Added a mockUseSorokitValue(overrides) helper (same pattern as TransactionHistory.test.tsx) whose client getter falls back to getClient(), and routed all 7 direct useSorokit mock sites through it.
• "disables the asset selector when no balances are loaded" asserted a value (XLM) that the current component never renders when the account is still loading (it shows the Loading assets… empty option). Renamed to reflect the real guard (disabled={state === "loading" || isLoadingAccount}) and asserts the disabled state + placeholder instead.

New acceptance-criteria tests (submit guard (#555))

• Send disabled with an empty destination — even a valid amount can't enable it; typing a valid destination does.
• Send disabled with an amount of 0 — shows "Amount must be greater than 0" and stays disabled until 0.0000001.
• Enter-key submission (via userEvent as the issue requests): Enter on the focused submit button opens the confirmation modal (default previewMode), and in previewMode={false} it submits directly with the correct { destination, amount }. jsdom does not implement implicit form submission (Enter inside a text field), so the keyboard path is driven through the focused submit button — the same event a browser's implicit submission produces.

Verification

• npx vitest run src/components/TransactionPanel.test.tsx → 37 passed (33 existing + 4 new), vs 11 failed | 22 passed on the untouched main baseline.
• npx eslint src/components/TransactionPanel.test.tsx → clean.

[drips-wave]

@BernardOnuh Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits