feat(tui): add markdown rendering support and toggle command

- Introduce new `owlen-markdown` crate that converts Markdown strings to `ratatui::Text` with headings, lists, bold/italic, and inline code.
- Add `render_markdown` config option (default true) and expose it via `app.render_markdown_enabled()`.
- Implement `:markdown [on|off]` command to toggle markdown rendering.
- Update help overlay to document the new markdown toggle.
- Adjust UI rendering to conditionally apply markdown styling based on the markdown flag and code mode.
- Wire the new crate into `owlen-tui` Cargo.toml.

crates/owlen-core/src/consent.rs

@@ -58,9 +58,14 @@ impl ConsentManager {
     /// Load consent records from vault storage
     pub fn from_vault(vault: &Arc<std::sync::Mutex<VaultHandle>>) -> Self {
         let guard = vault.lock().expect("Vault mutex poisoned");
-        if let Some(consent_data) = guard.settings().get("consent_records")
-            && let Ok(permanent_records) =
-                serde_json::from_value::<HashMap<String, ConsentRecord>>(consent_data.clone())
+        if let Some(permanent_records) =
+            guard
+                .settings()
+                .get("consent_records")
+                .and_then(|consent_data| {
+                    serde_json::from_value::<HashMap<String, ConsentRecord>>(consent_data.clone())
+                        .ok()
+                })
         {
             return Self {
                 permanent_records,
@@ -90,15 +95,19 @@ impl ConsentManager {
         endpoints: Vec<String>,
     ) -> Result<ConsentScope> {
         // Check if already granted permanently
-        if let Some(existing) = self.permanent_records.get(tool_name)
-            && existing.scope == ConsentScope::Permanent
+        if self
+            .permanent_records
+            .get(tool_name)
+            .is_some_and(|existing| existing.scope == ConsentScope::Permanent)
         {
             return Ok(ConsentScope::Permanent);
         }
 
         // Check if granted for session
-        if let Some(existing) = self.session_records.get(tool_name)
-            && existing.scope == ConsentScope::Session
+        if self
+            .session_records
+            .get(tool_name)
+            .is_some_and(|existing| existing.scope == ConsentScope::Session)
         {
             return Ok(ConsentScope::Session);
         }