docs: close OKF conformance gaps found by night audit

- references/okf-spec.md: replace v0.2 note with the deltas verified
  against upstream SPEC.md 2026-10-19 (timestamp->generated.at and
  # Citations->sources are the two breaking changes; trust fields and
  root-index okf_version are additive; bundle stays v0.1).
- index.md: restore the agentic-web-research section lost in the
  2026-08-28 rebuild and link log.md (index-coverage doctrine).
- gen-keybinds.sh emits OKF frontmatter so its generated artifact
  (tools/niri/keybindings.md, regenerated, 120 bindings) passes kb-lint;
  test added red->green.
- fix the two broken [[niri]] wikilinks (handy, noctalia-shell).

Refs #29

scripts/gen-keybinds.sh

@@ -27,6 +27,16 @@ KBD="${KBD:-$HOME/.config/niri/cfg/keybinds.kdl}"
 [ -f "$KBD" ] || { echo "error: no such file: $KBD" >&2; exit 1; }
 
 gen() {
+  echo "---"
+  echo "type: reference"
+  echo "title: Niri Keybindings"
+  echo "description: Live keybinding cheat sheet generated from $(basename "$KBD") — do not edit by hand."
+  echo "tags:"
+  echo "  - niri"
+  echo "  - keybindings"
+  echo "generated: { by: scripts/gen-keybinds.sh }"
+  echo "---"
+  echo
   echo "# Niri Keybindings"
   echo
   echo "> GENERATED by \`scripts/gen-keybinds.sh\` from \`$(basename "$KBD")\` — do not edit by hand."