🎨 Palette: Improve Team Lab unit selector UX with native constraints

[Gunnarguy]

Replaces manual Python-side validation and warning messages in the Team Lab unit selector with Streamlit's native max_selections=4 argument. Adds a helpful placeholder text for an improved empty-state UX.

Updates .Jules/palette.md to document the learning around native component constraints.

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PR created automatically by Jules for task 7631558248620112530 started by @Gunnarguy

Summary by Sourcery

Improve the Team Lab unit selector UX by enforcing selection limits via native Streamlit constraints and documenting the related design learning.

New Features:

• Add native max selection and placeholder support to the Team Lab unit multiselect for clearer, constraint-aware input.

Enhancements:

• Remove manual post-selection validation logic in favor of Streamlit's built-in max selection handling in the Team Lab view.

Documentation:

• Document the practice of using native frontend component constraints instead of Python-side validation in the Palette guidelines.

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[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Streamlit Team Lab unit selector now relies on native multiselect constraints and improved empty-state messaging, and palette documentation is updated to capture the learning about using native component limits.

Sequence diagram for updated Team Lab unit selection with native max_selections

sequenceDiagram
    actor User
    participant render_team_lab
    participant Streamlit_multiselect

    User->>render_team_lab: open Team Lab view
    render_team_lab->>Streamlit_multiselect: st.multiselect(max_selections=4, placeholder, help)
    User->>Streamlit_multiselect: select up to 4 units
    Streamlit_multiselect-->>render_team_lab: selected_variant_ids

    alt [no units selected]
        render_team_lab->>render_team_lab: st.info("Select up to 4 units to inspect SP economy and defensive coverage.")
        render_team_lab-->>User: return
    else [units selected]
        render_team_lab-->>User: continue with Team Lab analysis
    end

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File-Level Changes

Change	Details	Files
Use Streamlit multiselect native constraints instead of manual validation for the Team Lab unit selector and refine its UX text.	Replace manual Python-side length check and warning with the multiselect max_selections=4 argument so the UI prevents over-selection directly. Add a placeholder message to the multiselect to indicate the 4-unit limit before any selection is made. Update the help text to describe the purpose of selecting units (SP economy and defensive coverage) while still mentioning the 4-unit constraint. Remove logic that truncates the selected units list to the first four entries, relying on the frontend constraint instead.	src/grandchase_meta_analyzer/explorer_app.py
Document the guideline to prefer native Streamlit component constraints over manual validation in the Palette.	Add a new learning entry explaining why native component constraints (e.g., max_selections) give a better UX than post-hoc Python validation and warnings. Record an action item encouraging use of component features like max_selections, max_chars, and numeric bounds in Streamlit apps instead of invalid-input alerts.	.Jules/palette.md

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[sourcery-ai]

Hey - I've left some high level feedback:

• The empty-state st.info message, placeholder, and help text now all say essentially the same thing; consider differentiating them (e.g., guidance in help, concise hint in placeholder, and more contextual explanation in the info banner) to avoid redundant messaging.
• In .Jules/palette.md, the new 2024-05-18 entry appears after a 2025-06-17 entry; if the headings are meant to be chronological, consider reordering them to keep the timeline clear.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- The empty-state `st.info` message, placeholder, and help text now all say essentially the same thing; consider differentiating them (e.g., guidance in help, concise hint in placeholder, and more contextual explanation in the info banner) to avoid redundant messaging.
- In `.Jules/palette.md`, the new 2024-05-18 entry appears after a 2025-06-17 entry; if the headings are meant to be chronological, consider reordering them to keep the timeline clear.

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[Copilot]

Pull request overview

Improves the Team Lab “Units” selector UX by relying on Streamlit’s native selection constraints rather than post-selection Python validation, and captures the guideline in the Palette docs.

Changes:

• Enforce the 4-unit selection limit via st.multiselect(max_selections=4) and add placeholder/help text for clearer guidance.
• Remove the Python-side “truncate + warning” behavior for over-selection.
• Document the preference for native component constraints in .Jules/palette.md.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/grandchase_meta_analyzer/explorer_app.py	Uses max_selections=4 and improved empty-state guidance for the Team Lab unit selector.
.Jules/palette.md	Adds a documented UX guideline advocating native widget constraints over manual validation.