Step 5p6 lazy loading + Step 6b VM transpilation prep

Lazy module loading (Step 5 piece 6 completion):
- Add define-library wrappers + import declarations to 13 source .sx files
- compile-modules.js generates module-manifest.json with dependency graph
- compile-modules.js strips define-library/import before bytecode compilation
  (VM doesn't handle these as special forms)
- sx-platform.js replaces hardcoded 24-file loadWebStack() with manifest-driven
  recursive loader — only downloads modules the page needs
- Result: 12 modules loaded (was 24), zero errors, zero warnings
- Fallback to full load if manifest missing

VM transpilation prep (Step 6b):
- Refactor lib/vm.sx: 20 accessor functions replace raw dict access
- Factor out collect-n-from-stack, collect-n-pairs, pad-n-nils helpers
- bootstrap_vm.py: transpiles 9 VM logic functions to OCaml
- sx_vm_ref.ml: proof that vm.sx transpiles (preamble has stubs)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

web/lib/boot-helpers.sx

@@ -1,3 +1,11 @@
+(import (sx dom))
+(import (sx browser))
+(import (web adapter-dom))
+
+(define-library (web boot-helpers)
+  (export _sx-bound-prefix mark-processed! is-processed? clear-processed! callable? to-kebab sx-load-components call-expr base-env get-render-env merge-envs sx-render-with-env parse-env-attr store-env-attr resolve-mount-target remove-head-element set-sx-comp-cookie clear-sx-comp-cookie log-parse-error loaded-component-names csrf-token validate-for-request build-request-body abort-previous-target abort-previous track-controller track-controller-target new-abort-controller abort-signal apply-optimistic revert-optimistic dom-has-attr? show-indicator disable-elements clear-loading-state abort-error? promise-catch fetch-request fetch-location fetch-and-restore fetch-preload fetch-streaming dom-parse-html-document dom-body-inner-html create-script-clone cross-origin? browser-scroll-to with-transition event-source-connect event-source-listen bind-boost-link bind-boost-form bind-client-route-click sw-post-message try-parse-json strip-component-scripts extract-response-css sx-render sx-hydrate sx-process-scripts select-from-container children-to-fragment select-html-from-doc register-io-deps resolve-page-data parse-sx-data try-eval-content try-async-eval-content try-rerender-page execute-action bind-preload persist-offline-data retrieve-offline-data)
+  (begin
+
 (define _sx-bound-prefix "_sxBound")
 
 (define
@@ -764,3 +772,9 @@
 (define persist-offline-data (fn () nil))
 
 (define retrieve-offline-data (fn () nil))
+
+
+))
+
+;; Re-export to global env
+(import (web boot-helpers))