partial fix: Issues in the new experimental Planning mode #8432

Description

This issue compliments #8429 . Issues:

• Tools are unaware that the header property in the question tool has an upper limit of 12 chars. This leads to constant mis-calls, where the agent learns via trial-and-error (PR fixes)
• Editing a "Type your own answer" post-completion (i.e. you write an answer, go to the next question, and then go back) causes the following issues:
  1. firstly, the first option shows as selected.
  2. when re-selecting to edit, the TUI "spasms" between both the top line and the line where the cusor is on. This stops and corrects once the user modifies the content of the answer.

Plugins

None

OpenCode version

1.1.19

Steps to reproduce

1. When in plan mode, have the agent call the question tool
   • the agent will fail with "header must be <= 12 characters long". agent will call tool again
2. for one of the questions, fill it in with a "write your own" that will span at least two lines in your CLI
3. proceed to next question
4. go back to this question
   • will show the first answer selected insead of the custom one???
5. use arrows to select custom answer. hit enter
   • will proceed to next question. repeat step 3-5, except the second time round our answer will be selected, and pressing enter will finally enter edit mode for our answer
6. use arrows to go to the end of the answer. once first line has been scrolled past, TUI will flash between first line and currently-modifying line, as the TUI only has room for one line to appear visually
7. edit the input (so press any non-navigation key). input will now span required lines and act like normal again

Screenshot and/or share link

No response

Operating System

Ubuntu 24.04.3 LTS/Linux cascade 6.8.0-90-generic # 91-Ubuntu SMP PREEMPT_DYNAMIC Tue Nov 18 14:14:30 UTC 2025 x86_64 x86_64 x86_64 GNU/Linux

Terminal

bash via Kitty over ssh (also bash)