feat(search): add fuzzy search mode to search panel

[he666-ux]

Why

The roadmap already lists fuzzy search as a planned improvement for
plugin-search, and the current search panel only supports literal, whole-word,
and regexp matching. A fuzzy mode makes it easier to find approximate text when
the user only remembers a partial character sequence.

What Changes

• add a fuzzy search mode based on ordered subsequence matching
• add a Fuzzy toggle to the search panel
• make fuzzy mutually exclusive with regexp and wholeWord
• support Enter, Next, and Previous navigation for fuzzy matches
• disable All and replace controls in fuzzy mode to avoid ambiguous behavior in v1

Tests

• add matcher tests for fuzzy subsequence behavior
• add case-sensitive fuzzy search coverage
• add panel interaction tests for fuzzy toggle and mode exclusivity
• add navigation tests for Enter / Next / Previous under fuzzy mode
• add UI coverage for disabled select-all / replace controls in fuzzy mode

Validation

• pnpm test packages/plugin-search/test/plugin-search.test.ts
• pnpm --filter @floatboat/nexus-plugin-search build
• pnpm test

[CLAassistant]

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