Add paid-media category to scripts and CI workflow

Prepares infrastructure for the upcoming Paid Media Division (PR #83).
Registers paid-media in convert.sh, lint-agents.sh, install.sh, and
the lint-agents GitHub Actions workflow.

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

.github/workflows/lint-agents.yml

@@ -6,6 +6,7 @@ on:
       - 'design/**'
       - 'engineering/**'
       - 'marketing/**'
+      - 'paid-media/**'
       - 'product/**'
       - 'project-management/**'
       - 'testing/**'
@@ -27,7 +28,7 @@ jobs:
         id: changed
         run: |
           FILES=$(git diff --name-only --diff-filter=ACMR origin/${{ github.base_ref }}...HEAD -- \
-            'design/*.md' 'engineering/*.md' 'marketing/*.md' 'product/*.md' \
+            'design/*.md' 'engineering/*.md' 'marketing/*.md' 'paid-media/*.md' 'product/*.md' \
             'project-management/*.md' 'testing/*.md' 'support/*.md' \
             'spatial-computing/*.md' 'specialized/*.md' 'strategy/*.md')
           {