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/service/oauth/manager.rs

@@ -1,6 +1,9 @@
+//! OAuth 2.0 authorization-code + PKCE flow: token exchange and authorization URL building.
+
 use std::time::{SystemTime, UNIX_EPOCH};
 use serde::{Deserialize, Serialize};
 
+/// An OAuth access token plus its refresh token and absolute expiry (unix seconds).
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct OAuthToken {
     pub access_token: String,
@@ -12,6 +15,7 @@ pub struct OAuthToken {
 impl OAuthToken {
 }
 
+/// Static configuration for an OAuth provider: endpoints, client identity, and requested scopes.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct OAuthConfig {
     pub auth_url: String,
@@ -33,6 +37,7 @@ impl Default for OAuthConfig {
     }
 }
 
+/// Drives one OAuth flow: holds config, the current token (if any), and an HTTP client.
 pub struct OAuthManager {
     pub config: OAuthConfig,
     pub token: Option<OAuthToken>,
@@ -40,6 +45,7 @@ pub struct OAuthManager {
 }
 
 impl OAuthManager {
+    /// Create a manager for the given provider config with no token yet acquired.
     pub fn new(config: OAuthConfig) -> Self {
         OAuthManager {
             config,
@@ -48,6 +54,12 @@ impl OAuthManager {
         }
     }
 
+    /// Exchange an authorization code for an access token via the provider's token endpoint.
+    ///
+    /// Flow: POST form-encoded grant to `token_url` → parse JSON body →
+    /// compute absolute `expires_at` from `expires_in` → store on `self.token`.
+    ///
+    /// Return: `Err(String)` on network failure, non-2xx status, or a missing `access_token` field.
     pub fn exchange_code(&mut self, code: &str, redirect_uri: &str, code_verifier: &str) -> Result<(), String> {
         let mut params = std::collections::HashMap::new();
         params.insert("grant_type", "authorization_code");
@@ -83,13 +95,17 @@ impl OAuthManager {
         Ok(())
     }
 
+    /// Build the provider's authorization URL with PKCE and state params attached.
+    ///
+    /// Why: refuses to build a URL if `auth_url` is missing or invalid. Previously
+    /// this silently fell back to https://example.com, which produced a valid-looking
+    /// auth URL pointing at the wrong server and leaked client credentials in
+    /// query params. Returning an empty string signals failure to callers, who
+    /// can prompt the user to fix the OAuth config instead of starting a flow
+    /// against a wrong host.
+    ///
+    /// Return: the full authorization URL, or `""` if `auth_url` is empty/unparseable.
     pub fn build_auth_url(&self, redirect_uri: &str, state: &str, code_challenge: &str) -> String {
-        // Refuse to build a URL if `auth_url` is missing or invalid. Previously this
-        // silently fell back to https://example.com, which produced a valid-looking
-        // auth URL pointing at the wrong server and leaked client credentials in
-        // query params. Returning an empty string signals failure to callers, who
-        // can prompt the user to fix the OAuth config instead of starting a flow
-        // against a wrong host.
         let mut url = match url::Url::parse(&self.config.auth_url) {
             Ok(u) if !self.config.auth_url.is_empty() => u,
             _ => {