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.fish

@@ -182,7 +182,7 @@ function __config_settings_draw
 
     # ── Keybind hint ──────────────────────────────────────────────────────
     # string pad is width-aware (arrows count as 1 column)
-    set -l hint " ↑↓/kj move  ←→/hl set  Tab page  q quit"
+    set -l hint " ↑↓/kj move ←→/hl set Enter sub-cats Tab pg q quit"
     printf '%s│%s%s%s│\n' $p $c_dim (string pad -r -w $iw -- $hint) $c_reset
 
     # ── Bottom border ─────────────────────────────────────────────────────