fix(ci): replace fake action SHA pins (estate-wide niche sweep) (#15)

Comprehensive sweep across all niche fake SHAs found in the 2026-05-30
estate audit. Substitutions are version-faithful where the intended
version exists; bumped to nearest in-major where the version comment
was also hallucinated (e.g. v3.18.3 of action-slack didn't exist).

All real SHAs verified via gh api repos/<org>/<action>/commits/<sha>.

Provenance: project_estate_fake_action_sha_punch_list_2026_05_30.

Author: hyperpolymath

.github/workflows/e2e.yml

@@ -36,12 +36,12 @@ jobs:
         uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5  # v4
 
       - name: Setup Julia
-        uses: julia-actions/setup-julia@5c9647d97b78a5debe5164e9eec09d58c64f0a27  # v2
+        uses: julia-actions/setup-julia@fa02766e078afaaf09b14210362cee14137e6a32  # v2
         with:
           version: '1.10'
 
       - name: Julia cache
-        uses: julia-actions/cache@824243901fb567a0d7c9938c1d31e1f0bc1e65d9  # v2
+        uses: julia-actions/cache@d10a6fd8f31b12404a54613ebad242900567f2b9  # v2
 
       - name: Run Julia tests
         run: julia --project=. -e 'using Pkg; Pkg.test()'