Initial: desk + ncantu placeholder + per-project cursor configs

**Motivations:**
- Centraliser les fichiers Cursor (rules, skills, agents, commands, hooks) par user et par projet

**Root causes:**
- N/A

**Correctifs:**
- N/A

**Evolutions:**
- desk: rules, skills-cursor, agents, commands, hooks, argv/hooks/mcp.json
- ncantu: README placeholder
- 4NK_node, algo, builazoo, ia_local, lecoffre_ng, lecoffre_ng_pprod, lecoffre_ng_test: .cursor contents

**Pages affectées:**
- cursor/desk/, cursor/ncantu/, cursor/<project>/

algo/skills/document-improvement/examples.md

@@ -0,0 +1,40 @@
+# Document Improvement — Usage Examples
+
+## Launching as background task (mcp_task)
+
+To process a document in background, use `mcp_task` with `subagent_type="generalPurpose"` and a prompt like:
+
+```
+Improve and correct the document at [PATH] following the skill at .cursor/skills/document-improvement/SKILL.md.
+
+Read SKILL.md and reference.md from that directory, then apply the workflow:
+1. Analyze the document structure
+2. Process in chunks of ~1000 lines (or full document if < 1500 lines)
+3. Apply all corrections from the reference checklist
+4. Write edits directly to the file with search_replace
+
+Document path: v0/conjoncture_collatz.md
+```
+
+**With specific scope:**
+
+```
+Same as above, but only process lines 13800–13846 (last section).
+```
+
+## Direct invocation
+
+When the user says "améliore ce document" or "corrige le document X":
+
+1. Read `.cursor/skills/document-improvement/SKILL.md` and `reference.md`
+2. Follow the workflow in SKILL.md
+3. Process the document in chunks if needed
+
+## Chunk size guidelines
+
+| Document size | Strategy |
+|---------------|----------|
+| < 1500 lines | Single pass |
+| 1500–5000 lines | 2–4 chunks of ~1000 lines |
+| 5000–15000 lines | 5–15 chunks, break at section boundaries |
+| > 15000 lines | Multiple sessions; process ~3000–5000 lines per session |