fix(config-settings,docs): address final whole-branch review findings

Bundled fix wave for six findings from the sub-category-granularity
whole-branch review:

- config-settings: reset in_subcat on Tab/Shift-Tab so up/down keep
  routing to cur_row instead of freezing on the Sponge/Paths pages
  after a drill-down
- verify-manual: _parsed_components() now delegates to
  generate_component_registry.collect_components() instead of a
  lossy dict.update() merge, closing a taxonomy-check blind spot on
  identity collisions
- verify-manual: add test_committed_registry_matches_headers to
  catch the committed registry drifting from current # COMPONENT
  headers
- build-docs workflow: trigger on conf.d/** and config.fish edits,
  not just functions/**
- __config_settings_draw_subcat: show (Universal)/(Session) in the
  drill-down title so the persistence scope is visible before toggling
- __config_settings_draw / config-settings: mention the Enter
  sub-category drill-down in the on-screen hint and --help text
- generate_component_registry: send the "wrote ..." progress line to
  stderr so it no longer corrupts --concat's stdout output

functions/__config_settings_draw_subcat.fish

@@ -71,9 +71,19 @@ function __config_settings_draw_subcat
     set -l desc_w (math $iw - 34)
 
     set -l cat_label (string replace -r '^__fish_config_op_' '' -- $category_var)
-    set -l title_dashes (math $iw - (string length -- $cat_label) - 19)
-    printf '%s┌─%s Sub-categories: %s %s┐\n' \
-        $p $c_head "$cat_label$c_reset" (string repeat -n (math "max(0, $title_dashes)") '─')
+    # Scope indicator: toggling a row on this page writes -U (Universal,
+    # persistent) or -g (Session, this-shell-only) -- the title must say
+    # which, since it isn't otherwise visible anywhere on the page.
+    set -l scope_label Universal
+    test "$cur_scope" = session; and set scope_label Session
+    # Title layout is "┌─ Sub-categories: <label> (<scope>) ───┐"; the
+    # dash count must absorb every visible char added around cat_label so
+    # the line still totals iw+2, matching the surrounding box exactly --
+    # see the DESCRIPTION doc comment above for why this is hand-verified,
+    # not eyeballed.
+    set -l title_dashes (math $iw - (string length -- $cat_label) - (string length -- $scope_label) - 22)
+    printf '%s┌─%s Sub-categories: %s (%s)%s %s┐\n' \
+        $p $c_head "$cat_label" $scope_label "$c_reset" (string repeat -n (math "max(0, $title_dashes)") '─')
 
     printf '%s│%s│\n' $p $HBR