feat(token-tracking): repo aggregation via graph walk (task→workstream→repo)

By Repo now resolves via the full chain rather than requiring repo_id
directly on the token event:
  1. token_events.repo_id (direct)
  2. → workstreams.repo_id (via workstream_id)
  3. → task.workstream_id → workstreams.repo_id (via task_id)

Changes:
- Auto-populate repo_id on token events at creation time (both the
  token_events router and the tasks router)
- New GET /token-events/by-repo/ endpoint with RepoTokenSummary schema;
  returns tokens_in/out/total, event_count, by_model, by_note per repo
- Dashboard By Repo section uses /by-repo/ directly and shows repo_slug
  instead of a truncated UUID
- Backfilled the three existing events (userbased) with repo_id via SQL

185 tests pass.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

dashboard/src/token-cost.md

@@ -8,19 +8,22 @@ const POLL = 60_000;
 ```
 
 ```js
-// Live poll for token data
+// Fetch both /by-repo/ and raw events in parallel
 const tokenState = (async function*() {
   while (true) {
-    let data = {by_repo: [], by_workstream: [], top_tasks: [], by_model: [], total_events: 0}, ok = false;
+    let byRepo = [], events = [], ok = false;
     try {
-      const r = await fetch(`${API}/token-events/?limit=1000`);
-      ok = r.ok;
+      const [r1, r2] = await Promise.all([
+        fetch(`${API}/token-events/by-repo/`),
+        fetch(`${API}/token-events/?limit=1000`),
+      ]);
+      ok = r1.ok && r2.ok;
       if (ok) {
-        const events = await r.json();
-        data = buildSummary(events);
+        byRepo = await r1.json();
+        events = await r2.json();
       }
     } catch {}
-    yield {data, ok, ts: new Date()};
+    yield {byRepo, events, ok, ts: new Date()};
     await new Promise(res => setTimeout(res, POLL));
   }
 })();
@@ -28,15 +31,9 @@ const tokenState = (async function*() {
 
 ```js
 function buildSummary(events) {
-  const byRepo = {}, byWs = {}, byModel = {}, byTask = {};
+  const byWs = {}, byModel = {}, byTask = {};
   for (const e of events) {
     const tot = (e.tokens_in || 0) + (e.tokens_out || 0);
-    if (e.repo_id) {
-      byRepo[e.repo_id] = byRepo[e.repo_id] || {scope_id: e.repo_id, tokens_in: 0, tokens_out: 0, event_count: 0};
-      byRepo[e.repo_id].tokens_in += e.tokens_in || 0;
-      byRepo[e.repo_id].tokens_out += e.tokens_out || 0;
-      byRepo[e.repo_id].event_count++;
-    }
     if (e.workstream_id) {
       byWs[e.workstream_id] = byWs[e.workstream_id] || {scope_id: e.workstream_id, tokens_in: 0, tokens_out: 0, event_count: 0};
       byWs[e.workstream_id].tokens_in += e.tokens_in || 0;
@@ -55,7 +52,6 @@ function buildSummary(events) {
     .map(([k,v]) => typeof v === "number" ? {id: k, tokens_total: v} : {...v, tokens_total: (v.tokens_in||0)+(v.tokens_out||0)})
     .sort((a,b) => b.tokens_total - a.tokens_total);
   return {
-    by_repo: sortDesc(byRepo),
     by_workstream: sortDesc(byWs),
     by_model: Object.entries(byModel).map(([model,tokens_total]) => ({model,tokens_total})).sort((a,b)=>b.tokens_total-a.tokens_total),
     top_tasks: sortDesc(byTask).slice(0,10),
@@ -65,7 +61,8 @@ function buildSummary(events) {
 ```
 
 ```js
-const td = tokenState.data ?? {by_repo:[], by_workstream:[], top_tasks:[], by_model:[], total_events:0};
+const byRepo = tokenState.byRepo ?? [];
+const summary = buildSummary(tokenState.events ?? []);
 const _ok = tokenState.ok ?? false;
 const _ts = tokenState.ts;
 ```
@@ -74,7 +71,7 @@ const _ts = tokenState.ts;
 
 ```js
 const _liveEl = html`<div style="font-size:0.8rem;color:${_ok?'var(--theme-foreground-focus)':'red'}">
-  ● ${_ok ? `Live · ${_ts?.toLocaleTimeString()} · ${td.total_events} events` : "API offline"}
+  ● ${_ok ? `Live · ${_ts?.toLocaleTimeString()} · ${summary.total_events} events` : "API offline"}
 </div>`;
 display(_liveEl);
 ```
@@ -82,8 +79,8 @@ display(_liveEl);
 ## By Repo
 
 ```js
-if (td.by_repo.length === 0) {
-  display(html`<p style="color:var(--theme-foreground-muted)">No token events recorded yet.</p>`);
+if (byRepo.length === 0) {
+  display(html`<p style="color:var(--theme-foreground-muted)">No token events with repo association yet.</p>`);
 } else {
   display(Plot.plot({
     title: "Token consumption by repo",
@@ -94,9 +91,9 @@ if (td.by_repo.length === 0) {
     color: {legend: true, domain: ["tokens_in", "tokens_out"], range: ["#4e79a7","#f28e2b"]},
     marks: [
       Plot.barX(
-        td.by_repo.flatMap(r => [
-          {repo: r.scope_id.slice(0,8), type: "tokens_in", value: r.tokens_in},
-          {repo: r.scope_id.slice(0,8), type: "tokens_out", value: r.tokens_out},
+        byRepo.flatMap(r => [
+          {repo: r.repo_slug, type: "tokens_in",  value: r.tokens_in},
+          {repo: r.repo_slug, type: "tokens_out", value: r.tokens_out},
         ]),
         {x: "value", y: "repo", fill: "type", tip: true}
       ),
@@ -108,7 +105,7 @@ if (td.by_repo.length === 0) {
 ## By Workplan
 
 ```js
-const wsRows = td.by_workstream.slice(0, 20);
+const wsRows = summary.by_workstream.slice(0, 20);
 if (wsRows.length === 0) {
   display(html`<p style="color:var(--theme-foreground-muted)">No workstream data yet.</p>`);
 } else {
@@ -135,7 +132,7 @@ if (wsRows.length === 0) {
 ## By Model
 
 ```js
-if (td.by_model.length === 0) {
+if (summary.by_model.length === 0) {
   display(html`<p style="color:var(--theme-foreground-muted)">No model data yet.</p>`);
 } else {
   display(Plot.plot({
@@ -144,7 +141,7 @@ if (td.by_model.length === 0) {
     width: Math.min(700, width),
     x: {label: "Total tokens", tickFormat: "~s"},
     marks: [
-      Plot.barX(td.by_model, {x: "tokens_total", y: "model", fill: "#4e79a7", tip: true}),
+      Plot.barX(summary.by_model, {x: "tokens_total", y: "model", fill: "#4e79a7", tip: true}),
     ],
   }));
 }
@@ -153,10 +150,10 @@ if (td.by_model.length === 0) {
 ## Top 10 Tasks by Tokens
 
 ```js
-if (td.top_tasks.length === 0) {
+if (summary.top_tasks.length === 0) {
   display(html`<p style="color:var(--theme-foreground-muted)">No task-level data yet.</p>`);
 } else {
-  display(Inputs.table(td.top_tasks, {
+  display(Inputs.table(summary.top_tasks, {
     columns: ["task_id", "tokens_in", "tokens_out", "tokens_total"],
     header: {task_id: "Task ID", tokens_in: "In", tokens_out: "Out", tokens_total: "Total"},
     format: {