feat: stack insights tables vertically and paginate Pull requests table (#24198)

The "By model" and "Pull requests" tables on the PR Insights page
(`/agents/settings/insights`) were side-by-side at `lg` breakpoints, and
the Pull requests table was hard-capped at 20 rows by the backend.

- Replaced `lg:grid-cols-2` with a single-column stacked layout so both
tables span the full content width.
- Removed the `LIMIT 20` from the `GetPRInsightsRecentPRs` SQL query so
all PRs in the selected time range are returned.
- Can add this back if we need it. If we do, we should add a little
subheader above this table to indicate that we're not showing all PRs
within the selected timeframe.
- Added client-side pagination to the Pull requests table using
`PaginationWidgetBase` (page size 10), matching the existing pattern in
`ChatCostSummaryView`.
- Renamed the section heading from "Recent" to "Pull requests" since it
now shows the full set for the time range.
<img width="1481" height="1817" alt="image"
src="https://github.com/user-attachments/assets/0066c42f-4d7b-4cee-b64b-6680848edc68"
/>


> 🤖 PR generated with Coder Agents

coderd/database/queries.sql.go

@@ -3218,7 +3218,7 @@ func (q *sqlQuerier) GetPRInsightsPerModel(ctx context.Context, arg GetPRInsight
 	return items, nil
 }
 
-const getPRInsightsRecentPRs = `-- name: GetPRInsightsRecentPRs :many
+const getPRInsightsPullRequests = `-- name: GetPRInsightsPullRequests :many
 WITH pr_costs AS (
     SELECT
         prc.pr_key,
@@ -3238,9 +3238,9 @@ WITH pr_costs AS (
                     AND cds2.pull_request_state IS NOT NULL
               ))
         WHERE cds.pull_request_state IS NOT NULL
-          AND c.created_at >= $2::timestamptz
-          AND c.created_at < $3::timestamptz
-          AND ($4::uuid IS NULL OR c.owner_id = $4::uuid)
+          AND c.created_at >= $1::timestamptz
+          AND c.created_at < $2::timestamptz
+          AND ($3::uuid IS NULL OR c.owner_id = $3::uuid)
     ) prc
     LEFT JOIN LATERAL (
         SELECT COALESCE(SUM(cm.total_cost_micros), 0) AS cost_micros
@@ -3275,9 +3275,9 @@ deduped AS (
     JOIN chats c ON c.id = cds.chat_id
     LEFT JOIN chat_model_configs cmc ON cmc.id = c.last_model_config_id
     WHERE cds.pull_request_state IS NOT NULL
-      AND c.created_at >= $2::timestamptz
-      AND c.created_at < $3::timestamptz
-      AND ($4::uuid IS NULL OR c.owner_id = $4::uuid)
+      AND c.created_at >= $1::timestamptz
+      AND c.created_at < $2::timestamptz
+      AND ($3::uuid IS NULL OR c.owner_id = $3::uuid)
     ORDER BY COALESCE(NULLIF(cds.url, ''), c.id::text), c.created_at DESC, c.id DESC
 )
 SELECT chat_id, pr_title, pr_url, pr_number, state, draft, additions, deletions, changed_files, commits, approved, changes_requested, reviewer_count, author_login, author_avatar_url, base_branch, model_display_name, cost_micros, created_at FROM (
@@ -3305,17 +3305,16 @@ SELECT chat_id, pr_title, pr_url, pr_number, state, draft, additions, deletions,
     JOIN pr_costs pc ON pc.pr_key = d.pr_key
 ) sub
 ORDER BY sub.created_at DESC
-LIMIT $1::int
+LIMIT 500
 `
 
-type GetPRInsightsRecentPRsParams struct {
-	LimitVal  int32         `db:"limit_val" json:"limit_val"`
+type GetPRInsightsPullRequestsParams struct {
 	StartDate time.Time     `db:"start_date" json:"start_date"`
 	EndDate   time.Time     `db:"end_date" json:"end_date"`
 	OwnerID   uuid.NullUUID `db:"owner_id" json:"owner_id"`
 }
 
-type GetPRInsightsRecentPRsRow struct {
+type GetPRInsightsPullRequestsRow struct {
 	ChatID           uuid.UUID      `db:"chat_id" json:"chat_id"`
 	PrTitle          string         `db:"pr_title" json:"pr_title"`
 	PrUrl            sql.NullString `db:"pr_url" json:"pr_url"`
@@ -3337,24 +3336,20 @@ type GetPRInsightsRecentPRsRow struct {
 	CreatedAt        time.Time      `db:"created_at" json:"created_at"`
 }
 
-// Returns individual PR rows with cost for the recent PRs table.
+// Returns all individual PR rows with cost for the selected time range.
 // Uses two CTEs: pr_costs sums cost for the PR-linked chat and its
 // direct children (that lack their own PR), and deduped picks one row
-// per PR for metadata.
-func (q *sqlQuerier) GetPRInsightsRecentPRs(ctx context.Context, arg GetPRInsightsRecentPRsParams) ([]GetPRInsightsRecentPRsRow, error) {
-	rows, err := q.db.QueryContext(ctx, getPRInsightsRecentPRs,
-		arg.LimitVal,
-		arg.StartDate,
-		arg.EndDate,
-		arg.OwnerID,
-	)
+// per PR for metadata. A safety-cap LIMIT guards against unexpectedly
+// large result sets from direct API callers.
+func (q *sqlQuerier) GetPRInsightsPullRequests(ctx context.Context, arg GetPRInsightsPullRequestsParams) ([]GetPRInsightsPullRequestsRow, error) {
+	rows, err := q.db.QueryContext(ctx, getPRInsightsPullRequests, arg.StartDate, arg.EndDate, arg.OwnerID)
 	if err != nil {
 		return nil, err
 	}
 	defer rows.Close()
-	var items []GetPRInsightsRecentPRsRow
+	var items []GetPRInsightsPullRequestsRow
 	for rows.Next() {
-		var i GetPRInsightsRecentPRsRow
+		var i GetPRInsightsPullRequestsRow
 		if err := rows.Scan(
 			&i.ChatID,
 			&i.PrTitle,