feat: smart git URL parsing for browser URLs

- Add git URL parsing utilities (extract_base_repo_url, parse_git_url)
- Support GitHub, GitLab, Bitbucket browser URL detection
- Add /projects/repositories/parse-url endpoint
- Enhance repository creation to detect browser URLs and suggest corrections
- Add real-time URL validation in frontend with debouncing
- Show visual indicators (green/yellow/red) for URL validity
- Display inline suggestions with 'Use Suggested' button
- Add comprehensive unit tests for URL parsing
- Quality gates: ruff ✓, mypy ✓, typecheck ✓, lint ✓, build ✓

openspec/changes/smart-git-url-parsing/design.md

@@ -0,0 +1,154 @@
+# Smart Git URL Parsing - Design
+
+## Architecture
+
+```
+User pastes URL → Frontend validates → Backend validates → Clone repo
+                    ↓                      ↓
+            Show suggestions         Parse & suggest
+```
+
+## URL Detection Logic
+
+### Patterns to Detect
+
+1. **GitHub/GitLab/Bitbucket browser URLs**
+   - `https://github.com/owner/repo/tree/branch-name`
+   - `https://github.com/owner/repo/blob/branch/path/to/file`
+   - `https://github.com/owner/repo/pull/123`
+   - `https://gitlab.com/owner/repo/-/tree/branch`
+   - `https://bitbucket.org/owner/repo/src/branch/`
+
+2. **URLs with query parameters**
+   - `https://github.com/owner/repo?tab=readme-ov-file`
+   - `https://github.com/owner/repo.git?branch=develop`
+
+3. **Valid clone URLs (should pass through)**
+   - `https://github.com/owner/repo.git`
+   - `git@github.com:owner/repo.git`
+   - `https://github.com/owner/repo` (without .git)
+
+### URL Parsing Rules
+
+```python
+def extract_base_repo_url(url: str) -> str | None:
+    """Extract base repository URL from a browser/git URL.
+    
+    Examples:
+        https://github.com/user/repo/tree/main → https://github.com/user/repo.git
+        https://github.com/user/repo.git → https://github.com/user/repo.git
+        git@github.com:user/repo.git → git@github.com:user/repo.git
+        https://gitlab.com/user/repo/-/blob/main/README.md → https://gitlab.com/user/repo.git
+    
+    Returns None if URL doesn't match known patterns.
+    """
+    ...
+```
+
+**Algorithm:**
+1. Remove query parameters
+2. Detect host (github.com, gitlab.com, bitbucket.org, etc.)
+3. For GitHub: Remove `/tree/*`, `/blob/*`, `/pull/*`, `/issues/*` paths
+4. For GitLab: Remove `/-/tree/*`, `/-/blob/*` paths  
+5. For Bitbucket: Remove `/src/*` paths
+6. Ensure `.git` suffix
+7. Return cleaned URL or None
+
+## API Changes
+
+### POST /repositories (enhanced)
+
+**Request Body:**
+```json
+{
+  "project_id": "uuid",
+  "name": "my-repo",
+  "remote_url": "https://github.com/user/repo/tree/main",
+  "is_mirror": false
+}
+```
+
+**New Response for Non-Repo URLs (422):**
+```json
+{
+  "detail": "URL appears to be a browser URL, not a git clone URL",
+  "suggested_url": "https://github.com/user/repo.git",
+  "original_url": "https://github.com/user/repo/tree/main",
+  "needs_confirmation": true
+}
+```
+
+### New Endpoint: POST /repositories/parse-url
+
+**Request:**
+```json
+{
+  "url": "https://github.com/user/repo/tree/main"
+}
+```
+
+**Response:**
+```json
+{
+  "original_url": "https://github.com/user/repo/tree/main",
+  "base_url": "https://github.com/user/repo.git",
+  "is_valid_repo_url": false,
+  "needs_parsing": true,
+  "message": "This looks like a browser URL. Did you mean to clone https://github.com/user/repo.git?"
+}
+```
+
+## Frontend Flow
+
+### Repository Creation Dialog (Enhanced)
+
+1. **User pastes URL**
+2. **Frontend calls `/repositories/parse-url`** (debounced)
+3. **If URL needs parsing:**
+   - Show yellow warning indicator
+   - Display: "This looks like a browser URL"
+   - Show suggested URL with "Use this instead" button
+   - Allow user to proceed with original URL anyway
+4. **If URL is valid:**
+   - Show green checkmark
+   - Proceed normally
+5. **User clicks "Create"**
+6. **If backend returns 422 with suggestion:**
+   - Show confirmation dialog with suggested URL
+   - Options: "Use suggested URL", "Use original", "Cancel"
+
+### UI Components
+
+**URLInput Component:**
+- Input field with validation status icon
+- Shows inline suggestions when URL is detected as browser URL
+- Green/yellow/red border based on validation
+
+**URLCorrectionDialog Component:**
+- Modal dialog for confirming URL correction
+- Shows before/after comparison
+- Clear action buttons
+
+## Implementation Order
+
+1. **Backend utilities** - URL parsing functions with tests
+2. **Backend endpoint** - `/repositories/parse-url`  
+3. **Backend validation** - Enhanced POST /repositories with suggestion response
+4. **Frontend URL input** - Enhanced input with validation feedback
+5. **Frontend dialog** - Confirmation dialog for URL corrections
+6. **Integration** - Wire up parse-url endpoint to frontend
+7. **Tests** - Unit tests for URL parsing, integration tests for flow
+
+## Error Handling
+
+### Invalid URLs
+- Completely malformed URLs: Return 400 with clear message
+- Unsupported hosts: Return 400 with "Unsupported git host" 
+- Private repos (auth needed): Return 401/403 with auth instructions
+- Non-existent repos: Return 404 (from git clone failure)
+
+### Clone Failures
+- Network issues: Retry with exponential backoff
+- Auth required: Prompt for credentials
+- Large repos: Show progress indicator
+- Timeout: Increase timeout for large repos