docs: add wiki, complete lib nav, and rebuild mcp artifacts

- Add hand-written wiki (index, overview, how-to, extending, dev) with
  MkDocs config following the platform anatomy
- Complete the library nav by registering the csv and xlsx groups in
  docforge.nav.yml and docs/mkdocs.lib.yml
- Regenerate lib/MCP outputs with the rebuilt nav

docs/wiki/01_overview.md

@@ -0,0 +1,86 @@
+# 🧱 Overview
+
+OmniRead is designed as a **decoupled content engine** with three distinct
+layers. Understanding them is the key to using and extending the library.
+
+---
+
+## 🏗️ Architecture
+
+```text
+                 ┌─────────────────────────────┐
+                 │  Source (URL, file, storage) │
+                 └────────────┬────────────────┘
+                              │
+                    ┌─────────▼──────────┐
+                    │   Scraper / Client  │  fetches raw bytes
+                    └─────────┬──────────┘
+                              │  returns
+                    ┌─────────▼──────────┐
+                    │     Content         │  raw + source + type
+                    └─────────┬──────────┘
+                              │
+                    ┌─────────▼──────────┐
+                    │      Parser         │  parse() → structured T
+                    └────────────────────┘
+```
+
+1. **Scraper** (`BaseScraper`) — fetches raw bytes from a source (HTTP URL,
+   filesystem path, object storage). Returns a `Content` instance.
+   Scrapers never interpret content.
+2. **Content** (`Content`) — the canonical exchange model: raw bytes,
+   source identifier, and optional `ContentType` enum.
+3. **Parser** (`BaseParser[T]`) — receives a `Content` and returns a
+   structured result of type `T` via `parse()`.
+
+---
+
+## 📦 The `Content` model
+
+Defined in `omniread.core.content`:
+
+```python
+from dataclasses import dataclass
+from omniread import Content, ContentType
+
+@dataclass(slots=True)
+class Content:
+    raw: bytes
+    source: str
+    content_type: ContentType | None = None
+```
+
+- `raw` — the raw bytes exactly as retrieved.
+- `source` — URL, file path, or logical name identifying the origin.
+- `content_type` — optional `ContentType` enum value.
+
+---
+
+## 🎭 The `ContentType` enum
+
+| Value | MIME | Used by |
+|---|---|---|
+| `HTML` | `text/html` | HTMLScraper |
+| `PDF` | `application/pdf` | PDFScraper |
+| `XLSX` | `application/vnd.openxmlformats-...` | XlsxScraper |
+| `CSV` | `text/csv` | CsvScraper |
+| `JSON` | `application/json` | — |
+| `XML` | `application/xml` | — |
+
+---
+
+## 🧩 Format modules at a glance
+
+| Module | Scraper | Parser | Client | Notes |
+|---|---|---|---|---|
+| `omniread.html` | `HTMLScraper` | `HTMLParser` | — | httpx + BeautifulSoup |
+| `omniread.pdf` | `PDFScraper` | `PDFParser` | `FileSystemPDFClient` | explicit client layer |
+| `omniread.csv` | `CsvScraper` | `CsvParser` | `FileSystemCsvClient` | stdlib csv module |
+| `omniread.xlsx` | `XlsxScraper` | `XlsxParser` | `FileSystemXlsxClient` | openpyxl-backed |
+
+---
+
+## 📚 Read Next
+
+- [How to Use](02_how_to_use.md) — working examples per format.
+- [Extending OmniRead](03_extending.md) — subclassing scrapers and parsers.