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

tests/gen-keybinds.bats

@@ -63,6 +63,13 @@ teardown() {
   grep -q 'GENERATED' "$TMP/out/keybindings.md"
 }
 
+@test "output begins with OKF frontmatter so the artifact passes kb-lint" {
+  run "$GEN" "$TMP/keybinds.kdl"
+  [ "${lines[0]}" = '---' ]
+  [[ "${lines[1]}" == 'type: reference' ]]
+  grep -q '^generated:' <<<"$output"
+}
+
 @test "missing input file fails loudly" {
   run "$GEN" "$TMP/nope.kdl"
   [ "$status" -ne 0 ]