Rename Project Memory to Workspace Memory

Rename all references from "Project Memory" to "Workspace Memory" to avoid
future conflation if a "project" concept is introduced later.

Changes:
- Rename read_project_memory() -> read_workspace_memory()
- Update all prompts, tool descriptions, and comments
- Update header parsing in memory.rs to use "# Workspace Memory"
- Update display detection for "=== Workspace Memory ==="
- Update documentation and analysis/memory.md

11 files changed, ~36 occurrences updated.

crates/g3-core/src/tool_dispatch.rs

@@ -44,7 +44,7 @@ pub async fn dispatch_tool<W: UiWriter>(
         // Research tool
         "research" => research::execute_research(tool_call, ctx).await,
 
-        // Project memory tools
+        // Workspace memory tools
         "remember" => memory::execute_remember(tool_call, ctx).await,
 
         // ACD (Aggressive Context Dehydration) tools