refactor: flatten skills directory structure

- Restructure skills/research-zh and skills/research-en to flat layout
- Each skill now in its own directory (research, research-deep, etc.)
- Update installation: cp -r skills/research-zh/* ~/.claude/skills/
- Update command references from /research:deep to /research-deep

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

skills/research-en/research-add-fields/SKILL.md

@@ -0,0 +1,31 @@
+---
+user-invocable: true
+description: Add field definitions to existing research outline.
+allowed-tools: Bash, Read, Write, Glob, WebSearch, Task, AskUserQuestion
+---
+
+# Research Add Fields - Supplement Research Fields
+
+## Trigger
+`/research-add-fields`
+
+## Workflow
+
+### Step 1: Auto-locate Fields File
+Find `*/fields.yaml` file in current working directory, auto-read existing fields definitions.
+
+### Step 2: Get Supplement Source
+Ask user to choose:
+- **A. User direct input**: User provides field names and descriptions
+- **B. Web Search**: Launch agent to search common fields in this domain
+
+### Step 3: Display and Confirm
+- Display suggested new fields list
+- User confirms which fields to add
+- User specifies field category and detail_level
+
+### Step 4: Save Update
+Append confirmed fields to fields.yaml, save file.
+
+## Output
+Updated `{topic}/fields.yaml` file (in-place modification, requires user confirmation)