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/tool/git_cred.rs

@@ -1,9 +1,12 @@
+//! Tool wrapper around `git credential` for store/get/erase operations.
+
 use serde_json::{json, Value};
 use anyhow::{Result, anyhow};
 use std::process::Command;
 use super::Tool;
 use super::ToolCtx;
 
+/// Tool that shells out to `git credential <op>` to store, retrieve, or erase credentials.
 pub struct GitCred;
 
 impl Tool for GitCred {
@@ -29,6 +32,15 @@ impl Tool for GitCred {
         })
     }
 
+    /// Run `git credential <operation>`, forwarding stdin-less invocation to the git binary.
+    ///
+    /// Flow: extract `operation` arg → spawn `git credential <operation>` → capture output.
+    ///
+    /// Why: `store`/`get`/`erase` are the only credential-helper subcommands git supports;
+    /// no stdin is piped, so this mainly surfaces helper output/errors rather than
+    /// performing an interactive credential exchange.
+    ///
+    /// Return: combined stdout+stderr on success; error with stderr on non-zero exit.
     fn run(&self, _ctx: &ToolCtx, args: &Value) -> Result<String> {
         let operation = args.get("operation")
             .and_then(|v| v.as_str())