tui: optimistically render submitted prompts

[kitlangton]

Summary

• Insert submitted TUI chat prompts into the sync store immediately using the client-generated message/part IDs.
• Reuse those IDs for the actual prompt request so server events reconcile over the optimistic row.
• Remove the optimistic row if the prompt request fails before reconciliation.

Verification

• bun prettier --write packages/opencode/src/cli/cmd/tui/context/sync.tsx packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx
• bun typecheck from packages/opencode
• bun run lint packages/opencode/src/cli/cmd/tui/context/sync.tsx packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx reported existing warnings only
• bun run test -- src/cli/cmd/tui found no matching focused test files
• Pre-push hook was skipped after it failed in unrelated packages/enterprise bun:test type resolution during root bun turbo typecheck