ci(ai-validation): add :(glob) pathspec magic so top-level docs/*.md match

CRITICAL BUG discovered during smoke verify of PR #1977 (a draft PR
touching docs/quick-start.md). The prepare job ran SUCCESS but
validate SKIPPED because has_md_changes was false:

  $ git diff origin/rolling...HEAD --name-only -- 'docs/**/*.md'
  (empty)

  $ git diff origin/rolling...HEAD --name-only -- ':(glob)docs/**/*.md'
  docs/quick-start.md

Root cause: git's default pathspec syntax uses fnmatch with
FNM_PATHNAME (slashes are not crossed by `*`). The `**` glob is NOT
recognized in default pathspec — it's treated as plain `**`
(two consecutive asterisks). For `docs/**/*.md` this means git
requires at least one `/` between `docs/` and `*.md`, so:

  - docs/configuration/service/foo.md  → MATCHES   (1+ subdir)
  - docs/quick-start.md                 → NO MATCH (0 subdirs)
  - docs/index.md                       → NO MATCH (0 subdirs)
  - docs/cli.md                         → NO MATCH (0 subdirs)
  - docs/copyright.md                   → NO MATCH (0 subdirs)
  - docs/coverage.md                    → NO MATCH (0 subdirs)
  - docs/404.md                         → NO MATCH (0 subdirs)
  - docs/documentation.md               → NO MATCH (0 subdirs)

7 top-level files silently bypass validation on every PR that
touches them. Adding the `:(glob)` magic prefix opts in to true
shell-style ** semantics (also recognised by git's pathspec
parser per gitignore-pattern rules):

  - docs/**/*.md   →  :(glob)docs/**/*.md
  - docs/**/*.rst  →  :(glob)docs/**/*.rst

Three pathspec usages updated in the prepare job; comment references
to "docs/**/*.md" left unchanged (they read as informal shorthand).

Paired PR on VyOS-Networks/vyos-docs-opus-reviewer adjusts the
canonical scripts/ai-validation.yml identically.

0 files changed, 0 insertions, 0 deletions