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/fs/helpers.rs

@@ -1,7 +1,14 @@
+//! Shared helpers for filesystem tools: extracting string arguments from JSON
+//! and producing user-friendly "not found" diagnostics.
+
 use std::path::Path;
 use serde_json::Value;
 use anyhow::{Result, anyhow};
 
+/// Extract a required string argument from a JSON args map.
+///
+/// Return: the value as `String` if present and a string type; `Err` if missing
+/// or of a different JSON type (null, number, boolean, array, object).
 pub fn arg_str(args: &Value, name: &str) -> Result<String> {
     args.get(name)
         .and_then(|v| v.as_str())
@@ -9,6 +16,12 @@ pub fn arg_str(args: &Value, name: &str) -> Result<String> {
         .ok_or_else(|| anyhow!("missing required argument: {}", name))
 }
 
+/// Produce a user-friendly diagnostic string when a path doesn't resolve or exist.
+///
+/// Checks whether the resolved path canonically falls inside any workspace root
+/// and reports either "path outside workspaces" or "path does not exist" accordingly.
+///
+/// Return: a one-line description of the resolution failure.
 pub fn not_found_help(ctx: &super::super::ToolCtx, path: &Path, rel: &str) -> String {
     let canon = path.canonicalize().unwrap_or_else(|_| path.to_path_buf());
     let in_ws = ctx.workspaces.iter().any(|w| {