fix(ci): fix build-docs.yml's dead workflow reference, add permissions (#179)

Two issues in the same file:

- It called reqstool/.github/.github/workflows/build-docs.yml, which
  doesn't exist -- the actual file is common-build-docs.yml, as every
  other repo in the org already references. This workflow has been
  failing on every docs-path push or PR since 2026-06-23, unrelated to
  any recent migration.
- CodeQL flagged the missing permissions block
  (actions/missing-workflow-permissions). common-build-docs.yml itself
  only requires contents: read, so that's what the caller now grants.

Signed-off-by: Jimisola Laursen <jimisola@jimisola.com>

Author: jimisola

.github/workflows/build-docs.yml

@@ -10,6 +10,9 @@ on:
     paths:
       - "docs/**"
 
+permissions:
+  contents: read
+
 jobs:
   build:
-    uses: reqstool/.github/.github/workflows/build-docs.yml@main
+    uses: reqstool/.github/.github/workflows/common-build-docs.yml@main