docs(proposals): static asset cache-busting plan

Proposes a one-liner Jinja helper that appends ?v=<commit-sha> to
static JS/CSS URLs, leveraging the existing build_info pipeline so
users no longer need to hard-reload after every deploy. Documents the
codemod scope (143 callsites), open decisions, and the server-side
Cache-Control: immutable follow-up that makes the version flip pay off.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

mkdocs.yml

@@ -351,6 +351,7 @@ nav:
       - RBAC Cleanup Two-Phase Plan: proposals/rbac-cleanup-two-phase-plan.md
       - Security Audit Demo POC Builder: proposals/security-audit-demo-poc-builder.md
       - Security Hardening Plan: proposals/security-hardening-plan.md
+      - Static Asset Cache-Busting: proposals/static-asset-cache-busting.md
       - Store Login Platform Detection: proposals/store-login-platform-detection.md
       - Store Menu Multi-Platform Visibility: proposals/store-menu-multi-platform-visibility.md
       - Storefront Builder Vision: proposals/storefront-builder-vision.md