Make ottyl_seq/ottyl_ts usable in dashboard PromQL queries (ticket 055)

evaluate_promql previously resolved every metric name through bucket_values,
which only returns data for a real MetricDeclaration — so a dashboard panel
querying ottyl_seq/ottyl_ts/ottyl_fmt (already supported in the filter bar
and alert conditions) silently returned an empty series. ottyl_seq/ottyl_ts
are now synthesized directly from the ingested-log index instead of requiring
a declaration; ottyl_fmt is categorical (json/logfmt/none) with no sensible
numeric reading, so it's rejected up front with a clear error pointing back
at the filter bar rather than returning nothing.

GET /api/params now also lists the three reserved names (marked `reserved:
true`, distinct from `auto_derived`) purely for discoverability — merged in
at the API layer only, not the engine's internal ParamDeclarations query, so
profile-switch removal and metric-param-promotion logic are unaffected.
declare_param also now rejects declaring a param under one of these names.

Docs.tsx and the Params panel are updated to reflect the new dashboard
support and the reserved/non-editable listing.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XFUNZwCvz3kcod3352ZR2o

webapp/src/components/Docs.tsx

@@ -105,6 +105,9 @@ const SECTIONS: DocSection[] = [
           <Code>ottyl_seq</Code>, <Code>ottyl_ts</Code>, and <Code>ottyl_fmt</Code> are reserved metric names present
           on every log line, so they're always filterable without declaring anything. <Code>ottyl_fmt</Code> holds the
           auto-detected format of the line's text — <Code>json</Code>, <Code>logfmt</Code>, or <Code>none</Code>.
+          They also appear (flagged <Code>reserved</Code>) in <Code>GET /api/params</Code> for discoverability, though
+          there's no UI to edit or remove them — see also <em>Dashboards</em> below for using{' '}
+          <Code>ottyl_seq</Code>/<Code>ottyl_ts</Code> in a panel query.
         </p>
         <p className="font-semibold text-text">Date/time formats</p>
         <p>Timestamp comparisons accept three forms:</p>
@@ -335,6 +338,14 @@ const SECTIONS: DocSection[] = [
           Dashboards are saved per profile, so they travel with it when you switch or copy it — an active profile is
           required to create or save one; pick or create one from the settings menu first.
         </p>
+        <p>
+          The reserved <Code>ottyl_seq</Code>/<Code>ottyl_ts</Code> names (see <em>Filtering</em> above) work in panel
+          queries the same as any declared metric — e.g. <Code>count(ottyl_seq)</Code> for log volume, or{' '}
+          <Code>rate(ottyl_ts[1m])</Code> for ingest rate — since every log line carries them without a metric
+          declaration. <Code>ottyl_fmt</Code> is categorical (<Code>json</Code>/<Code>logfmt</Code>/<Code>none</Code>
+          ), not a number, so it's rejected in a panel query with an explicit error rather than silently charting
+          nothing — filter on it in the filter bar instead.
+        </p>
       </div>
     ),
   },

webapp/src/components/Params.tsx

@@ -49,6 +49,12 @@ export function Params({ params, onDeclared }: { params: ParamDeclaration[]; onD
   // original (and anything referencing it by name) rather than renaming it.
   const [editingName, setEditingName] = useState<string | null>(null)
 
+  // `reserved` params (`ottyl_seq`/`ottyl_ts`/`ottyl_fmt`) are synthesized server-side purely for
+  // discoverability (see `GET /api/params`) — they aren't real declarations, so they're kept out of
+  // the editable/clickable list and shown separately, non-interactively.
+  const declaredParams = useMemo(() => params.filter((p) => !p.reserved), [params])
+  const reservedParams = useMemo(() => params.filter((p) => p.reserved), [params])
+
   const isBoolean = kind === 'boolean'
   const isElapsedSinceLast = source === 'elapsed_since_last'
   // The message match regex doubles as a sample line here so a pasted JSON log line unlocks the
@@ -264,8 +270,10 @@ export function Params({ params, onDeclared }: { params: ParamDeclaration[]; onD
         <div className="min-w-0 flex-1">
           <div className="mb-1 text-xs text-text-subtle">Declared params</div>
           <div className="flex flex-wrap gap-1">
-            {params.length === 0 && <span className="text-xs text-text-faint">No params declared yet.</span>}
-            {params.map((p) => (
+            {declaredParams.length === 0 && (
+              <span className="text-xs text-text-faint">No params declared yet.</span>
+            )}
+            {declaredParams.map((p) => (
               <button
                 key={p.name}
                 type="button"
@@ -287,6 +295,24 @@ export function Params({ params, onDeclared }: { params: ParamDeclaration[]; onD
               </button>
             ))}
           </div>
+          {reservedParams.length > 0 && (
+            <>
+              <div className="mb-1 mt-2 text-xs text-text-subtle">
+                Reserved (built in — present on every line, not editable)
+              </div>
+              <div className="flex flex-wrap gap-1">
+                {reservedParams.map((p) => (
+                  <span
+                    key={p.name}
+                    className="rounded border border-dashed border-border-soft px-2 py-1 text-xs text-text-faint"
+                    title={`${p.name} (${p.kind}, reserved)`}
+                  >
+                    {p.name} ({p.kind})
+                  </span>
+                ))}
+              </div>
+            </>
+          )}
         </div>
       </div>
     </div>