fix(file-explorer): align default exclusions with VS Code

[wsp1911]

Summary

• Align default file-tree exclusions with VS Code's built-in baseline.
• Show dotfiles, IDE metadata, dependency directories, and build outputs by default.
• Keep .git, .svn, .hg, .DS_Store, and Thumbs.db excluded.
• Add a Rust contract test for the default visibility behavior.

Fixes #

Type and Areas

Type:

bug fix / UI/UX / test

Areas:

Rust core, desktop/Tauri, web UI

Motivation / Impact

The workspace explorer previously hid a broad hard-coded set of project directories such as target, node_modules, dist, and .vscode. It now follows VS Code's narrower built-in exclusion baseline, making project files and generated outputs visible by default.

The follow-up work for user-configurable glob exclusions, .gitignore handling, persistence, and remote-rule unification is intentionally out of scope.

Verification

• pnpm run fmt:rs
• cargo test -p bitfun-services-core default_tree_visibility_matches_vscode_baseline
• pnpm run type-check:web
• git diff --check

Reviewer Notes

This change only updates default visibility. Search filtering and remote SSH directory filtering remain unchanged.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.