Module indexer 

Workspace walker: Markdown notes, optional Canvas, optional Rust AST.

WorkspaceIndexer is the engine behind crate::Brain::sync. It owns a Database, walks the workspace (skipping target/, .git/, etc.), and:

1. Upserts Markdown nodes transactionally (FTS + tags + aliases + edges)
2. Indexes Obsidian Canvas relationships when the obsidian feature is on
3. Extracts Rust symbols when the ast feature is on
4. Resolves pending WikiLink / symbol: targets
5. Compiles .brain/graph.mmap when the mmap feature is on

Structs

WorkspaceIndexer

Indexes a workspace directory into a Database.