fix: copy packages/ to Docker build context (fixes HF Spaces build #30)

* docs: spec #30 - HF Spaces build error missing packages/ directory

* fix: copy packages/ to docker build context before pip install (fixes HF Spaces build)

Root cause: Dockerfile copied requirements.txt but not packages/ directory.
pip install failed because ./packages/niivueviewer path didn't exist.

Changes:
- Dockerfile: Add COPY packages/ before pip install
- .dockerignore: Add standard exclusions, keep node_modules out of context

Note: Do NOT ignore scripts/ - deepisles_adapter.py is required by Dockerfile.

.dockerignore

@@ -0,0 +1,33 @@
+# Docker ignore file
+__pycache__/
+*.pyc
+*.pyo
+*.pyd
+.Python
+env/
+venv/
+.venv/
+.git/
+.github/
+.vscode/
+.idea/
+.DS_Store
+*.egg-info/
+.mypy_cache/
+.pytest_cache/
+.ruff_cache/
+.coverage
+htmlcov/
+dist/
+build/
+site/
+docs/_build/
+
+# Ignore local data and test artifacts
+data/
+results/
+tests/
+# NOTE: Do NOT ignore scripts/ - deepisles_adapter.py is needed by Dockerfile
+
+# Ignore node_modules in custom components to keep build context small
+**/node_modules/

Dockerfile

@@ -31,6 +31,10 @@ WORKDIR /home/user/demo
 # Copy requirements first for better layer caching
 COPY --chown=1000:1000 requirements.txt /home/user/demo/requirements.txt
 
+# Copy local packages (Custom Components) BEFORE pip install
+# This is required because requirements.txt refers to ./packages/niivueviewer
+COPY --chown=1000:1000 packages/ /home/user/demo/packages/
+
 # Install Python dependencies into SYSTEM Python (NOT conda env)
 # DeepISLES conda env is Python 3.8, but Gradio 6 needs Python 3.10+
 # We'll shell out to conda env for inference only

docs/specs/30-bug-hf-spaces-build-packages-dir.md

@@ -0,0 +1,116 @@
+# Spec #30: HF Spaces Build Error - Missing packages/ Directory
+
+## Status: 🔴 P0 BLOCKER
+
+## Issue
+HuggingFace Spaces Docker build fails with:
+```
+ERROR: Invalid requirement: './packages/niivueviewer': Expected package name at the start of dependency specifier
+    ./packages/niivueviewer
+    ^ (from line 28 of requirements.txt)
+Hint: It looks like a path. File './packages/niivueviewer' does not exist.
+```
+
+## Root Cause Analysis
+
+### Timeline
+1. PR #29 added `gradio_niivueviewer` custom component in `packages/niivueviewer/`
+2. Added `./packages/niivueviewer` to `requirements.txt` line 28 for local installs
+3. Dockerfile copies `requirements.txt` but NOT `packages/` directory
+4. `pip install -r requirements.txt` fails because path doesn't exist
+
+### Architecture Gap
+```
+Local Development:
+  requirements.txt → ./packages/niivueviewer → ✅ EXISTS
+
+HF Spaces Docker:
+  COPY requirements.txt → Container
+  pip install -r requirements.txt
+  → ./packages/niivueviewer → ❌ NOT COPIED
+```
+
+## Solution Options
+
+### Option A: Copy packages/ in Dockerfile (Recommended)
+Add `COPY --chown=1000:1000 packages/ /home/user/demo/packages/` before pip install.
+
+**Pros:**
+- Simple fix
+- Preserves local development workflow
+- Editable install works correctly
+
+**Cons:**
+- Adds ~1.3MB to Docker image (compiled JS bundle)
+
+### Option B: Build wheel and include in Docker
+Pre-build wheel, copy to container, install from wheel file.
+
+**Pros:**
+- More "production" approach
+
+**Cons:**
+- More complex build process
+- Need to manage wheel artifacts
+
+### Option C: Separate requirements files
+Create `requirements-docker.txt` without local path dependencies.
+
+**Pros:**
+- Clear separation of concerns
+
+**Cons:**
+- Duplicate maintenance
+- Easy to drift out of sync
+
+## Recommended Fix
+
+**Option A** - Simple, maintainable, aligns with how local development works.
+
+### Implementation
+
+```dockerfile
+# BEFORE pip install, add:
+COPY --chown=1000:1000 packages/ /home/user/demo/packages/
+```
+
+### Full Dockerfile Change
+
+```dockerfile
+# Copy requirements first for better layer caching
+COPY --chown=1000:1000 requirements.txt /home/user/demo/requirements.txt
+
+# Copy custom component packages (required for pip install)
+COPY --chown=1000:1000 packages/ /home/user/demo/packages/
+
+# Install Python dependencies into SYSTEM Python
+RUN pip install --no-cache-dir -r requirements.txt
+```
+
+## Test Plan
+
+### Level 1: Local Docker Build
+```bash
+docker build -t stroke-demo-test .
+docker run -p 7860:7860 stroke-demo-test
+```
+
+### Level 2: HF Spaces Deploy
+Push to HF Spaces, verify build succeeds and app loads.
+
+### Level 3: Functional Test
+- Upload NIfTI files
+- Run segmentation
+- Verify NiiVue 3D viewer renders volumes
+
+## Files to Modify
+- `Dockerfile` - Add COPY for packages/ directory
+
+## Risk Assessment
+- **Low risk** - Additive change, doesn't modify existing code
+- **Reversible** - Can easily remove if issues arise
+
+## Acceptance Criteria
+- [ ] HF Spaces build succeeds
+- [ ] App loads without "Loading..." hang
+- [ ] NiiVue viewer displays volumes correctly