feat(02-02): add code block borders with syntax highlighting and GFM table grid

- emit_code_block: ╭─ {lang} ─╮ / │ content │ / ╰──╯ rounded borders; lang label in Yellow; content via highlight_code()
- emit_table: ┌┬┐├┼┤└┴┘ full box-drawing grid; bold LightCyan header row; Left/Right/Center cell alignment
- Rename stub methods to emit_code_block_now / emit_table_now (clean naming; delegates to full emitters)
- Remove unused push_fg / push_fg_mod helper methods
- cargo check passes; 19 expected dead_code warnings (modules wired in Plan 03)

src/renderer.rs

@@ -92,18 +92,6 @@ impl RenderState {
         self.style_stack.push(new_style);
     }
 
-    /// Push a completely new foreground-colored style.
-    fn push_fg(&mut self, color: Color) {
-        let new_style = Style::default().fg(color);
-        self.style_stack.push(new_style);
-    }
-
-    /// Push a new style with a foreground color and modifier.
-    fn push_fg_mod(&mut self, color: Color, modifier: Modifier) {
-        let new_style = Style::default().fg(color).add_modifier(modifier);
-        self.style_stack.push(new_style);
-    }
-
     // ── Line flushing ─────────────────────────────────────────────────────────
 
     /// Flush `current_spans` into a `Line`, optionally prepending blockquote borders.
@@ -184,20 +172,22 @@ impl RenderState {
         self.push_blank();
     }
 
-    // ── Code block stub ───────────────────────────────────────────────────────
-    // (will be replaced in Task 2 with full border + highlighting)
+    // ── Code block emitter ────────────────────────────────────────────────────
 
-    fn emit_code_block_stub(&mut self) {
+    /// Flush the accumulated code buffer and emit a bordered, syntax-highlighted
+    /// code block into `self.lines`.
+    fn emit_code_block_now(&mut self) {
         let code = std::mem::take(&mut self.code_buf);
         let lang = std::mem::take(&mut self.code_lang);
         let width = self.width;
         emit_code_block(&code, &lang, width, &mut self.lines);
     }
 
-    // ── Table stub ────────────────────────────────────────────────────────────
-    // (will be replaced in Task 2 with full box-drawing grid)
+    // ── Table emitter ─────────────────────────────────────────────────────────
 
-    fn emit_table_stub(&mut self) {
+    /// Flush the accumulated table rows and emit a full box-drawing grid table
+    /// into `self.lines`.
+    fn emit_table_now(&mut self) {
         let alignments = std::mem::take(&mut self.table_alignments);
         let rows = std::mem::take(&mut self.table_rows);
         emit_table(&alignments, &rows, &mut self.lines);
@@ -284,7 +274,7 @@ fn handle_event(state: &mut RenderState, event: Event) {
         }
         Event::End(TagEnd::CodeBlock) => {
             state.in_code_block = false;
-            state.emit_code_block_stub();
+            state.emit_code_block_now();
         }
 
         // ── Lists ─────────────────────────────────────────────────────────────
@@ -388,7 +378,7 @@ fn handle_event(state: &mut RenderState, event: Event) {
         }
         Event::End(TagEnd::Table) => {
             state.in_table = false;
-            state.emit_table_stub();
+            state.emit_table_now();
         }
         Event::Start(Tag::TableHead) => {
             state.in_table_head = true;