fix(feishu): address second-round codex bot review feedback

P1 - Reject single oversized subtrees in batch insert (docx-batch-insert.ts):
  A first-level block whose descendant count exceeds BATCH_SIZE (1000) cannot
  be split atomically (e.g. a very large table). Previously such a block was
  silently added to the current batch and sent as an oversized request,
  violating the API limit. Now throws a descriptive error so callers know to
  reduce the content size.

P2 - Preserve unmatched brackets in color markup parser (docx-color-text.ts):
  Text like 'Revenue [Q1] up' contains a bracket pair with no matching '[/...]'
  closer. The original regex dropped the '[' character in this case, silently
  corrupting the text. Fixed by appending '|\[' to the plain-text alternative
  so any '[' that does not open a complete tag is captured as literal text.

extensions/feishu/src/docx-batch-insert.ts

@@ -128,6 +128,16 @@ export async function insertBlocksInBatches(
     const descendants = collectDescendants(blocks, [firstLevelId]);
     const newBlocks = descendants.filter((b) => !usedBlockIds.has(b.block_id));
 
+    // A single block whose subtree exceeds the API limit cannot be split
+    // (a table or other compound block must be inserted atomically).
+    if (newBlocks.length > BATCH_SIZE) {
+      throw new Error(
+        `Block "${firstLevelId}" has ${newBlocks.length} descendants, which exceeds the ` +
+          `Feishu API limit of ${BATCH_SIZE} blocks per request. ` +
+          `Please split the content into smaller sections.`,
+      );
+    }
+
     // If adding this first-level block would exceed limit, start new batch
     if (
       currentBatch.blocks.length + newBlocks.length > BATCH_SIZE &&

extensions/feishu/src/docx-color-text.ts

@@ -55,11 +55,13 @@ interface Segment {
  */
 export function parseColorMarkup(content: string): Segment[] {
   const segments: Segment[] = [];
-  // Match [tag]...[/tag] or plain text between tags.
-  // The closing tag name is intentionally not validated against the opening tag:
-  // mismatched tags like [red]text[/green] are treated as [red]text[/red] —
-  // the opening tag's style is applied and the closing tag is consumed.
-  const tagPattern = /\[([^\]]+)\](.*?)\[\/(?:[^\]]+)\]|([^[]+)/gs;
+  // Match [tag]...[/tag], plain text, or a bare '[' that is not part of a
+  // complete tag pair.  Without the trailing `|\[` fallback, a '[' that has no
+  // matching '[/...]' closer (e.g. "[Q1]" with no "[/...]") would be silently
+  // dropped, corrupting the surrounding text.  The closing tag name is not
+  // validated against the opening tag: [red]text[/green] is treated as
+  // [red]text[/red] — opening tag style applies, closing tag is consumed.
+  const tagPattern = /\[([^\]]+)\](.*?)\[\/(?:[^\]]+)\]|([^[]+|\[)/gs;
   let match;
 
   while ((match = tagPattern.exec(content)) !== null) {