feat: Add GitHub as a browsable location provider

[BrianLeishman]

Summary

Add GitHub as a location provider so users can paste a GitHub link and browse repositories, branches, files, releases, and gists like a filesystem — the same way Google Drive and SMB shares work today.

URI Scheme

github://owner/repo/tree/branch/path/to/file
github://owner/gists/

Mirrors GitHub URL structure. Could also detect and convert github.com URLs pasted into the path bar.

Virtual Root Structure

Per-repo virtual folders (similar to Google Drive's My Drive, Shared drives, etc.):

• Code — default branch file tree (landing view)
• Branches — list all branches → browse each branch's tree
• Releases — list releases → browse downloadable assets
• Gists — at user level (github://owner/gists/) — list and browse gist files

Capabilities

Capability	Supported	Notes
Read	Yes	Public repos immediately; private repos via auth
Write	Limited	Create/delete files via Contents API, create releases
Create directories	No	Git doesn't have empty directories
Delete	Limited	Delete files via Contents API
Rename	Limited	Delete + create via Contents API
Copy	No	Not a native GitHub concept
Move	No	Delete + create
Watching	No	requiresExplicitRefresh: true
Thumbnails	Yes	Download to temp → generate locally (same pattern as gdrive)

Technical Notes

Provider Architecture

Follows the existing LocationProvider trait pattern:

• New module: src-tauri/src/locations/github/ with mod.rs, provider.rs, auth.rs
• Register in provider registry at src-tauri/src/locations/mod.rs (same pattern as gdrive/smb registration around lines 26-40)
• Scheme: github

Authentication

Options (in priority order):

1. gh CLI token — gh auth token gives an existing PAT if the user has gh installed. Zero-friction for developers.
2. OAuth Device Flow — GitHub's device flow for users without gh CLI. Similar to the Google Drive OAuth flow in src-tauri/src/locations/gdrive/auth.rs.
3. No auth — public repos work without authentication (lower rate limits).

API

GitHub REST API v3 (via octocrab or reqwest):

• GET /repos/{owner}/{repo}/git/trees/{branch}?recursive=1 — file tree
• GET /repos/{owner}/{repo}/contents/{path}?ref={branch} — file/directory contents
• GET /repos/{owner}/{repo}/branches — list branches
• GET /repos/{owner}/{repo}/releases — list releases
• GET /repos/{owner}/{repo}/releases/{id}/assets — release assets
• GET /users/{owner}/gists — list gists
• PUT /repos/{owner}/{repo}/contents/{path} — create/update file
• DELETE /repos/{owner}/{repo}/contents/{path} — delete file

Cross-Provider Paste

New cases in paste_items_to_location() in src-tauri/src/commands.rs (around line 2230+):

("github", "file")   → download file via Contents API raw URL → copy to local path
("file", "github")   → upload via Contents API PUT
("github", "gdrive") → download to temp → upload to gdrive
("gdrive", "github") → download to temp → upload via Contents API
("github", "smb")    → download to temp → upload_file_to_smb()
("smb", "github")    → download_file_from_smb() to temp → upload via Contents API
("github", "github") → same-provider: provider.copy() (create via Contents API)

Thumbnail Generation

Add github handling in src-tauri/src/thumbnails/generators/mod.rs — download file to temp directory (same pattern as gdrive thumbnails), then call generate_local().

Frontend

• Sidebar (src/components/Sidebar.tsx): New "GitHub" section with GitHub icon, add repo button, list of connected repos/accounts
• Path bar: Detect github.com URLs and convert to github:// scheme in normalizePath() in src/store/useAppStore.ts
• Types (src/types/index.ts): May need remote_id, download_url fields on FileItem (already exist from gdrive support)

Acceptance Criteria

• LocationProvider trait implemented for github scheme
• Can browse public repos without auth
• Can authenticate via gh CLI token or OAuth device flow for private repos
• Virtual folders: Code (default branch), Branches, Releases, Gists
• Can navigate into branches and browse file trees
• Can download/open files from GitHub repos
• Thumbnails generate for supported file types (images, PDFs, etc.)
• Cross-provider paste works (github↔file, github↔gdrive, github↔smb)
• Sidebar shows GitHub section with add/remove repo UI
• Path bar accepts github.com URLs and converts to github:// scheme
• Release assets are downloadable
• Registered in provider registry and all existing commands work automatically