feat: eager vLLM warmup and smart page titles in paginate stage

- Add warmup() to LlmProvider interface for eager subprocess startup
- ManagedVllmProvider.warmup() starts vLLM in background on project load
- ProviderRegistry.warmupAll() triggers all managed providers
- NamedProvider proxies warmup() to inner provider
- paginate stage generates LLM-powered descriptive page titles when
  available, cached by content hash, falls back to generic "Page N"
- project-mcp-endpoint calls warmupAll() on router creation so vLLM
  is loading while the session initializes

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

README.md

@@ -150,6 +150,81 @@ mcpctl get all --project monitoring -o yaml > backup.yaml
 mcpctl apply -f backup.yaml
 ```
 
+## Content Pipeline (ProxyModel)
+
+ProxyModel defines a **content transformation pipeline** that runs between upstream MCP servers and the client (e.g., Claude). It processes tool results, prompts, and resources through ordered stages before delivering them.
+
+### Built-in Models
+
+| Model | Stages | Use case |
+|-------|--------|----------|
+| **default** | `passthrough` → `paginate` (8KB pages) | Safe pass-through with pagination for large responses |
+| **subindex** | `section-split` → `summarize-tree` | Splits large content into sections, returns a summary index. Client drills down with `_resultId`/`_section` params |
+
+### How `subindex` Works
+
+1. Upstream returns a large tool result (e.g., 50KB of device states)
+2. `section-split` divides content into logical sections (2KB–15KB each)
+3. `summarize-tree` generates a compact index with section summaries (~200 tokens each)
+4. Client receives the index and can request specific sections via `_section` parameter
+
+### Configuration
+
+Set per-project (all servers use the same model):
+
+```yaml
+kind: Project
+metadata:
+  name: home-automation
+spec:
+  servers: [home-assistant, node-red]
+  proxyModel: subindex
+```
+
+Override per-server within a project:
+
+```yaml
+kind: Project
+metadata:
+  name: monitoring
+spec:
+  servers: [grafana, prometheus]
+  proxyModel: default
+  serverOverrides:
+    grafana:
+      proxyModel: subindex
+```
+
+Via CLI:
+
+```bash
+mcpctl create project monitoring --server grafana --server prometheus --proxy-model subindex
+```
+
+### Custom ProxyModels
+
+Place YAML files in `~/.mcpctl/proxymodels/` to define custom pipelines:
+
+```yaml
+kind: ProxyModel
+metadata:
+  name: my-pipeline
+spec:
+  stages:
+    - type: section-split
+      config:
+        minSectionSize: 1000
+        maxSectionSize: 10000
+    - type: summarize-tree
+      config:
+        maxTokens: 150
+        maxDepth: 2
+  appliesTo: [toolResult, prompt]
+  cacheable: true
+```
+
+Inspect available models: `mcpctl get proxymodels` / `mcpctl describe proxymodel subindex`
+
 ## Resources
 
 | Resource | What it is | Example |