Convert planner hook into zustand store

[Choollol]

Summary

Test Plan

• Planner data is fetched correctly without any errors
• Planner features still work, like filtering courses and search with Planner

Issues

Closes #1646

[cubic-dev-ai]

2 issues found across 8 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="apps/antalmanac/src/components/RightPane/CoursePane/SearchForm/AdvancedSearch/AdvancedSearchTextFields.tsx">

<violation number="1" location="apps/antalmanac/src/components/RightPane/CoursePane/SearchForm/AdvancedSearch/AdvancedSearchTextFields.tsx:185">
P1: Calling `updateTakenCourses` on selection change without clearing it in the invalid-roadmap reset path can leave stale taken-course filtering enabled after the UI resets the selection.</violation>
</file>

<file name="apps/antalmanac/src/stores/PlannerStore.ts">

<violation number="1" location="apps/antalmanac/src/stores/PlannerStore.ts:71">
P1: Clear `plannerRoadmaps` when roadmap fetch fails to avoid serving stale roadmap data after an error.</violation>
</file>

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