Create detailed implementation plan for migrating overflow menus to ha-dropdown

[Copilot]

Breaking change

Proposed change

Adds a comprehensive migration plan document (MIGRATION_PLAN_HA_DROPDOWN.md) for converting all overflow menus from legacy ha-button-menu/ha-md-button-menu to the new ha-dropdown component.

Scope identified:

• ~44 files using ha-button-menu + ha-list-item
• 20 files using ha-md-button-menu + ha-md-menu-item

Plan structure:

• Phase 1: 23 PRs for mwc-based ha-button-menu migration
• Phase 2: 10 PRs for ha-md-button-menu migration
• Phase 3: 1 PR for deprecation cleanup
• Each PR contains 1-3 related files max

Migration pattern documented:

Old	New
ha-button-menu/ha-md-button-menu	ha-dropdown
ha-list-item/ha-md-menu-item	ha-dropdown-item
slot="graphic"/slot="start"	slot="icon"
class="warning"	variant="danger"
@click handlers	value + @wa-select

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (thank you!)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Example configuration

# N/A - documentation only

Additional information

• This PR is related to issue or discussion: Use ha-dropdown for automations/scripts #28293, Migrate ha-button-menu to ha-dropdown in 4 files #28300, Migrate ha-button-menu to ha-dropdown in 3 files #28337

Checklist

• The code change is tested and works locally.
• There is no commented out code in this PR.
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

Original prompt

Create a detailed implementation plan for migrating all overflow menus to ha-dropdown.

Checkout the already done migrations in the PRs #28293, #28300 and #28337

Each migration PR should migrate max 3 files, the best would be that the files are maybe related. The migration should be done with one PR after another.

At first we should migrate all mwc based ha-button-menu with ha-list-item to ha-dropdown with ha-dropdown-item.

When this is done let's migrate all ha-md-button-menu with ha-md-menu-item to ha-dropdown with ha-dropdown-item.

Don't forget to migrate also the deviders. Carefully check the styles. ha-dropdown itself cannot be really styled as I understood it. When it needs to be placed absolute for example we should style the trigger instead.

Summary: Plan a migration, each step has 3-4 files max and each step should be a PR. But don't create any PR yet. We do it step by step. First the Plan and then step by step each PR

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