PR #16301 - onyx-dot-app/onyx

Description

#16242 moved sections/knowledge/SourceHierarchyBrowser.tsx to Opal SelectButton. That file was the last caller of @/refresh-components/buttons/SelectButton, so nothing imports the refresh component now. The only references left were its own story and lint config.

This PR removes:

web/src/refresh-components/buttons/SelectButton.tsx and SelectButton.stories.tsx.
Its two baseline entries in web/.oxlintrc.json.
Its row in web/tools/oxlint/opal/rules/no-replaced-refresh-import.ts. The rule's comment says to delete the row when the refresh module is deleted.
The src/refresh-components/buttons floor in web/.type-coverage-baseline.yaml, lowered from 99.7 to 99.6. The deleted file was fully typed, so the directory ratio fell by a rounding step.

How Has This Been Tested?

bun run types:check: no type errors.
bunx oxlint: no new errors.
Pre-commit hooks (oxfmt, oxlint, type coverage, feature-map integrity) pass.

Additional Options

[Optional] Please cherry-pick this PR to the latest release version.

Link to Devin session: https://app.devin.ai/sessions/ba1242cc5338467c8db2fdfa02b81d10
Open in Devin Desktop: https://app.devin.ai/desktop/session/ba1242cc5338467c8db2fdfa02b81d10?variant=devin

Summary by cubic

Removes the now-unused SelectButton from refresh-components after #16242 moved the last caller to Opal's component.

Deletes SelectButton.tsx and its story file, along with its lint baseline entries.
Removes the SelectButton row from the no-replaced-refresh-import rule.
Lowers the type coverage baseline for src/refresh-components/buttons from 99.7 to 99.6, since the removed file was fully typed.

Summary by CodeRabbit

Removed
- Removed the SelectButton component and its Storybook examples.
- Removed support for tracking SelectButton as a design-system and layout baseline item.
- Removed related replacement guidance for SelectButton imports.
Maintenance
- Adjusted the type-coverage threshold for refresh button components.