Add local folder picker and git ref comboboxes

[Modsofthenation]

Rebased onto latest main (includes the graph/3D work from #13).

The repository field still accepts a pasted path. Browse opens an in-app explorer of the local filesystem so you can pick a git root without typing it.

Base and head stay free-text (paste a SHA, HEAD~1, a branch name). The chevron opens a dropdown of common refs, branches, tags, and the 50 most recent commits for that repo.

Changes

• GET /api/fs lists directories (git roots are marked)
• GET /api/git/refs returns branches, tags, and the 50 most recent commits
• Toolbar browse button + explorer dialog
• Base/head comboboxes that keep typed values

Review follow-ups applied on rebase

• Cap how many directory entries the picker scans so huge folders cannot hang the API
• Treat git worktrees (.git file) as roots in the explorer
• Resolve refs from a subdirectory of a work tree, not only from the git root
• Rebuild bundled static assets to match

Tests

• Unit coverage for directory listing and git ref parsing
• API coverage for both endpoints
• Playwright: browse to a repo, type a ref, pick a commit and a branch from the menus

  

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Review details

⚙️ Run configuration

Configuration used: defaults

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Run ID: d0166f76-163c-4008-a613-333e4f0f8cc9

📥 Commits

Reviewing files that changed from the base of the PR and between 019a0f9 and fbe178e.

📒 Files selected for processing (19)

• src/loadpath/server/app.py
• src/loadpath/static/assets/LayeredGraph3D-CoG8lubm.js
• src/loadpath/static/assets/index-DVQVwbDy.js
• src/loadpath/static/assets/index-aoV_COFI.js
• src/loadpath/static/assets/index-fLLLv9tC.css
• src/loadpath/static/index.html
• src/loadpath/workspace.py
• tests/e2e/test_api_flow.py
• tests/e2e/test_ui_flows.py
• tests/unit/test_workspace.py
• ui/src/App.tsx
• ui/src/RefCombobox.tsx
• ui/src/RepoExplorer.tsx
• ui/src/api.ts
• ui/src/icons.tsx
• ui/src/refs.test.ts
• ui/src/refs.ts
• ui/src/styles.css
• ui/src/types.ts

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