docs: correct the difficulty_ladder integration contract, drop dead check

CLAUDE.md

@@ -22,13 +22,23 @@ reading state straight off the Host's `window.highway` object.
   see `feedBack/static/js/session.js`'s comment on `showScreen()` re:
   feedBack#923/#924. Patching `window.showScreen` here would silently never
   fire for real navigation; this was an actual regression until fixed.
-- **No bespoke API with `feedback-plugin-dynamic-difficulty`.** Both plugins
-  independently read the same Host surface (`highway.getPhrases()` /
-  `hasPhraseData()` / `getMastery()`) for section-difficulty data — this
-  plugin works whether or not dynamic_difficulty is installed, as long as
-  *something* populates that phrase data. Don't reach into
-  dynamic_difficulty's own globals/localStorage directly; go through
-  `window.highway`.
+- **Section-difficulty data comes from `difficulty_ladder`'s
+  `difficulty:sections-updated` event, not independent `highway` reads
+  (issue #63).** This plugin used to independently read `highway.getPhrases()`
+  / `hasPhraseData()` / `getMastery()` for section-difficulty data — that
+  changed when the glass-fill rendering was rewritten to consume
+  `difficulty_ladder`'s emitted event instead (`_smUpdateDifficultyFills` /
+  `_smGetSectionDifficulty` just render whatever `fillPercentage` /
+  `glassSize` the event's payload carries per section). This plugin still
+  works standalone with no ladder plugin installed — `_smIsDynamicDifficultyAvailable()`
+  gates the subscription on `window._ddCapabilities`, absent means no
+  glasses are shown, not an error — but when a ladder plugin *is* installed,
+  this is the API, not a coincidence of both sides reading the same Host
+  state. See `difficulty_ladder`'s `INTEGRATION.md` for the full contract
+  (fill formula, fallback/timing behavior). Load order matters: plugins load
+  alphabetically, so `difficulty_ladder` (< `section_map`) sets
+  `window._ddCapabilities` before this plugin's one-time availability check
+  runs.
 - **Seeking must go through the Host's canonical funnel**
   (`window.feedBack.seek` / `window.slopsmith.seek`, wrapped by `_smSeek`),
   not by poking `audio.currentTime` directly — see the comment on `_smSeek`

plugin.json

@@ -1,7 +1,7 @@
 {
   "id": "section_map",
   "name": "Section Map",
-  "version": "1.2.4",
+  "version": "1.2.5",
   "private": false,
   "script": "screen.js",
   "category": "practice",

screen.js

@@ -49,12 +49,17 @@ function _smGetColor(name) {
     return SM_COLORS.default;
 }
 
-// Check if dynamic-difficulty plugin is installed and available
+// Check if the difficulty_ladder plugin (formerly "dynamic-difficulty") is
+// installed and available. `window._ddCapabilities` is the compatibility
+// marker it sets at load time (see difficulty_ladder's screen.js and
+// INTEGRATION.md, issue #63) -- the marker name predates that plugin's
+// rename from `dynamic_difficulty` to `difficulty_ladder`, kept as-is since
+// it's the established capability-marker contract between the two plugins.
+// (A second check here used to also probe `window.feedBackViz_dynamic_difficulty`,
+// a viz-factory-naming-convention global difficulty_ladder never actually
+// set even before the rename -- dead since this function was written.)
 function _smIsDynamicDifficultyAvailable() {
     if (typeof window.feedBack === 'undefined') return false;
-    // Check if dynamic-difficulty is in the active plugins list or has exposed a capability
-    if (typeof window.feedBackViz_dynamic_difficulty !== 'undefined') return true;
-    // Additional check: look for dynamic-difficulty's global scope if available
     if (typeof window._ddCapabilities !== 'undefined') return true;
     return false;
 }