feat(#2789): trim skill description anti-patterns; enforce 100-char budget (#2823)

* feat(#2789): trim skill description anti-patterns; enforce 100-char budget

- Trim descriptions in all commands/gsd/*.md files over 100 chars
- Remove flag documentation from descriptions (belongs in argument-hint)
- Remove Triggers: keyword stuffing
- Add scripts/lint-descriptions.cjs — fails on descriptions > 100 chars
- Add npm script: lint:descriptions
- Add tests/enh-2789-description-budget.test.cjs

Closes #2789

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* docs(#2789): add CHANGELOG entry for description budget lint

* docs(#2789): update COMMANDS.md descriptions; add skill description standards note

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/lint-descriptions.cjs

@@ -0,0 +1,83 @@
+#!/usr/bin/env node
+/**
+ * lint-descriptions.cjs
+ *
+ * Enforces the 100-char description budget for commands/gsd/*.md files.
+ *
+ * Usage:
+ *   node scripts/lint-descriptions.cjs [file.md ...]
+ *
+ * If no args are given, scans commands/gsd/ automatically.
+ * Exits 1 if any description exceeds 100 chars; exits 0 if all pass.
+ */
+
+'use strict';
+
+const fs = require('fs');
+const path = require('path');
+
+const MAX_LENGTH = 100;
+const COMMANDS_DIR = path.join(__dirname, '..', 'commands', 'gsd');
+
+/**
+ * Parse the description field from frontmatter in a .md file.
+ * Returns null if no description is found.
+ */
+function parseDescription(content) {
+  const fmMatch = content.match(/^---\r?\n([\s\S]*?)\r?\n---/);
+  if (!fmMatch) return null;
+  const fm = fmMatch[1];
+
+  const quoted = fm.match(/^description:\s+"((?:[^"\\]|\\.)*)"\s*$/m);
+  if (quoted) return quoted[1];
+
+  const plain = fm.match(/^description:\s+(.+)$/m);
+  if (plain) return plain[1].trim();
+
+  return null;
+}
+
+function getFiles() {
+  if (process.argv.length > 2) {
+    return process.argv.slice(2);
+  }
+  return fs.readdirSync(COMMANDS_DIR)
+    .filter(f => f.endsWith('.md'))
+    .map(f => path.join(COMMANDS_DIR, f));
+}
+
+const files = getFiles();
+const violations = [];
+
+for (const filePath of files) {
+  let content;
+  try {
+    content = fs.readFileSync(filePath, 'utf-8');
+  } catch (err) {
+    process.stderr.write(`ERROR: Cannot read file: ${filePath}\n  ${err.message}\n`);
+    process.exit(1);
+  }
+
+  const description = parseDescription(content);
+  if (description === null) continue;
+
+  if (description.length > MAX_LENGTH) {
+    violations.push({ filePath, length: description.length, description });
+  }
+}
+
+if (violations.length === 0) {
+  const checked = files.length;
+  process.stdout.write(`ok lint-descriptions: ${checked} file(s) checked, 0 violations\n`);
+  process.exit(0);
+}
+
+process.stderr.write(`\nERROR lint-descriptions: ${violations.length} violation(s) found\n\n`);
+for (const v of violations) {
+  const preview = v.description.length > 120 ? v.description.slice(0, 117) + '...' : v.description;
+  process.stderr.write(`  ${v.filePath}\n`);
+  process.stderr.write(`    Length : ${v.length} (max ${MAX_LENGTH})\n`);
+  process.stderr.write(`    Desc   : ${preview}\n\n`);
+}
+process.stderr.write(`Trim descriptions to <= ${MAX_LENGTH} chars. Flag docs belong in argument-hint:.\n\n`);
+process.exit(1);