feat: add APIEmbedder for remote embedding with multi-endpoint support

- Introduced APIEmbedder class to handle embeddings via a remote HTTP API.
- Implemented token packing to optimize batch sizes based on token limits.
- Added support for multiple API endpoints with round-robin dispatching.
- Included retry logic for API calls with exponential backoff on failures.
- Enhanced indexing pipeline with file exclusion checks and smart chunking strategies.
- Updated tests to cover new APIEmbedder functionality and ensure robustness.

.claude/skills/workflow-lite-plan/SKILL.md

@@ -554,12 +554,25 @@ Skill("lite-execute")
 ├── explorations-manifest.json        # Exploration index
 ├── planning-context.md               # Evidence paths + understanding
 ├── plan.json                         # Plan overview (task_ids[])
+├── test-checklist.json               # Generated by lite-test-review
+├── test-review.md                    # Generated by lite-test-review
 └── .task/
     ├── TASK-001.json
     ├── TASK-002.json
     └── ...
 ```
 
+## Chain: lite-plan → lite-execute → lite-test-review
+
+```
+lite-plan (LP-Phase 1-5)
+  └─ Skill("lite-execute")     ← executionContext (global)
+       ├─ Step 1-4: Execute + Review
+       └─ Step 5: Skill("lite-test-review")  ← testReviewContext (global)
+            ├─ TR-Phase 1-4: Test + Fix
+            └─ TR-Phase 5: Report + Sync specs
+```
+
 ## 12. Error Handling
 
 | Error | Resolution |