Refactor: upgrade to latest MCP and docx-rs; add Router, fonts CLI, and builder-based DOCX edits

- Integrate mcp-server Router with mcp-spec and expose tools
- Add fonts subcommands (download/verify) with pinned sources + checksums
- Replace deprecated docx-rs APIs; rebuild DOCX via ops (paragraphs/headings/tables/lists/page breaks/headers/footers)
- Implement proper numbered lists via docx-rs numbering
- Gate advanced features behind `advanced-docx` for future porting
- Resolve lopdf and image import ambiguities; adapt search and responses

Cargo.toml

@@ -24,6 +24,7 @@ exclude = [
 # Official MCP SDK
 mcp-server = "0.1"
 mcp-core = "0.1"
+mcp-spec = "0.1"
 
 # Async runtime
 tokio = { version = "1.40", features = ["full"] }
@@ -100,6 +101,7 @@ wkhtmltopdf = { version = "0.4", optional = true }
 [features]
 default = ["embedded-fonts", "pure-rust-pdf"]
 runtime-server = []
+advanced-docx = []
 embedded-fonts = []
 pure-rust-pdf = []
 external-tools = ["headless_chrome", "wkhtmltopdf"]