fix(security): harden skill apply and activation flows

Restrict auto-apply to trusted review comments so spoofed issue comments
cannot write optimized SKILL.md content into pull request branches.

Reject activation symlinks that escape the source root and add
regression coverage for both security checks.

tools/scripts/tests/apply_skill_optimization_security.test.js

@@ -0,0 +1,43 @@
+const assert = require('node:assert');
+const path = require('node:path');
+
+const repoRoot = path.resolve(__dirname, '..', '..', '..');
+const {
+  selectLatestTrustedReviewComment,
+} = require(path.join(repoRoot, 'tools', 'scripts', 'apply_skill_optimization.cjs'));
+
+const trustedMaintainerComment = {
+  body: '## Tessl Skill Review\ntrusted maintainer content',
+  author_association: 'MEMBER',
+  user: { login: 'maintainer-user', type: 'User' },
+};
+
+const spoofedUserComment = {
+  body: '## Tessl Skill Review\nspoofed content',
+  author_association: 'NONE',
+  user: { login: 'random-user', type: 'User' },
+};
+
+const trustedBotComment = {
+  body: '## Tessl Skill Review\nbot content',
+  author_association: 'NONE',
+  user: { login: 'github-actions[bot]', type: 'Bot' },
+};
+
+assert.strictEqual(
+  selectLatestTrustedReviewComment([trustedMaintainerComment, spoofedUserComment]),
+  trustedMaintainerComment,
+  'the apply script must ignore later untrusted review comments',
+);
+
+assert.strictEqual(
+  selectLatestTrustedReviewComment([spoofedUserComment, trustedBotComment]),
+  trustedBotComment,
+  'the apply script should accept review comments from the configured trusted bot',
+);
+
+assert.strictEqual(
+  selectLatestTrustedReviewComment([spoofedUserComment]),
+  null,
+  'the apply script must reject untrusted review comments entirely',
+);