feat: clone a remote repository and add it as a project

[HrushikeshAnandSarangi]

Adds a "Clone from remote" action next to Add project (sidebar, bottom bar, command palette): paste a URL, pick/edit a destination folder, watch git clone progress in a small panel with inline auth/exists/network error reporting, and land on the same registered-project state Add project produces today.

Closes #97

What changed

• Backend (src-tauri/src/git_clone.rs, new): check_clone_target does a non-authoritative pre-flight check for an existing non-empty destination folder; git_clone_repo spawns git clone --progress, streams stderr line-by-line to the frontend as git-clone:log events (tagged with a request id), and returns either the cloned path or the raw git stderr on failure. Follows the same "shell out to the system git binary" convention as every other git command in lib.rs — no new crate dependency.
• Pure logic (src/lib/gitClone.ts): parses pasted URLs (https, ssh, and the scp-like git@host:owner/repo form) into a default destination folder name, and classifies raw git stderr into auth / exists / network / unknown for the UI. Covered by src/lib/gitClone.check.ts.
• UI (src/components/CloneRepoModal.tsx): form → streaming-progress → error-with-retry modal, modeled on the existing NewProjectModal / AtlasIndexModal. On success it hands the cloned path back to the same openProjectByPath flow "Add project" already uses, so registration/opening behavior is identical.
• Entry points: a second icon next to "Add project" in the sidebar header and bottom bar (WorkspaceView/LeftSidebar.tsx), plus a "Clone from Remote" entry in the command palette (CommandPalette.tsx).
• Auth for private repos relies entirely on whatever git already has configured on the machine (SSH key, credential helper, gh auth) — no new credential UI.

Related issue

Closes #97

How was this tested

• npx tsc --noEmit — clean.
• cargo check — clean.
• npm test — 11/11 self-checks pass, including new src/lib/gitClone.check.ts (URL parsing across https/ssh/scp-like shapes incl. self-hosted host+port, and error classification across all four categories against real git/OpenSSH stderr strings).

Checklist

• npx tsc --noEmit passes
• cargo check passes (if backend changed)
• I've tested this on my OS — noted which: Windows
• Docs updated if user-facing behaviour changed
• No secrets, tokens, or personal paths in the diff

[vercel]

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