docs(framework): canonize merge-authority policy (hard gate 13 + E2E gate note)

Coordinated work: post-review merge go-ahead belongs to the active
coordinator/orchestrator session; solo delivery merges without routine
confirmation as before. 'No self-merge' means no UNREVIEWED self-merge.

Previously this policy existed only as per-host local patches to the
preserved ~/.config/mosaic/AGENTS.md (web1 + sb-it-mgr-0-lt rule 38) and
was lost from E2E-DELIVERY.md on every framework sync. Shipping it in
defaults/AGENTS.md + guides/E2E-DELIVERY.md makes it permanent for fresh
installs and upgrades.

Policy: Jason, 2026-06-11.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/mosaic/framework/guides/E2E-DELIVERY.md

@@ -88,6 +88,11 @@ For implementation work, you MUST run this cycle in order:
 
 ### Post-PR Hard Gate (Execute Sequentially, No Exceptions)
 
+> **Merge authority:** if a coordinator/orchestrator session is active for this
+> work, obtain the coordinator's merge go-ahead after review passes, then run
+> the gate (AGENTS.md hard gate "Merge authority"). Solo delivery proceeds
+> without asking.
+
 1. `~/.config/mosaic/tools/git/ci-queue-wait.sh --purpose merge -B main`
 2. `~/.config/mosaic/tools/git/pr-merge.sh -n <PR_NUMBER> -m squash`
 3. `~/.config/mosaic/tools/git/pr-ci-wait.sh -n <PR_NUMBER>`