Enhance tool documentation and add new features

- Added module-level documentation for memory tools (`remember`, `recall`, `forget`) to clarify their purpose.
- Improved documentation in `recall.rs` and `remember.rs` to describe the functionality and flow of memory entry operations.
- Updated `mod.rs` to include descriptions for the tool trait and execution context.
- Enhanced `plan.rs` with detailed comments on plan-mode signaling tools.
- Documented text search tools in `search.rs` to explain their functionality.
- Improved sequential-thinking tool documentation in `seqthink.rs`.
- Added safety filter documentation in `shell_filter` for credential and git operations.
- Enhanced utility tools documentation, including `cd`, `dir_cache_update`, and `todowrite`.
- Improved rendering documentation in view modules (`chat`, `markdown`, `status`, `workflow`) to clarify rendering flows and purposes.

src/model/msglog/mod.rs

@@ -1,3 +1,6 @@
+//! SQLite-backed message log: per-session `messages.sqlite` storing chat
+//! messages, blobs, and archive/summary metadata.
+
 pub mod blobs;
 pub mod query;
 pub mod schema;
@@ -5,6 +8,14 @@ pub mod schema;
 pub use blobs::store_blob;
 pub use query::insert_message;
 
+/// Open (creating if needed) a session's `messages.sqlite` and ensure its
+/// schema is initialized.
+///
+/// Flow: resolve `<session_dir>/messages.sqlite` → create parent dirs →
+/// open a SQLite connection → run `schema::init_schema`.
+///
+/// Return: an open, schema-ready `Connection`, or an error if any step
+/// fails.
 pub fn open_or_create(session_dir: &std::path::Path) -> anyhow::Result<rusqlite::Connection> {
     let path = session_dir.join("messages.sqlite");
     if let Some(parent) = path.parent() {