feat: add e2e workspace build duration metric (#21739)

Adds coderd_template_workspace_build_duration_seconds histogram that
tracks the full duration from workspace build creation to agent ready.
This captures the complete user-perceived build time including
provisioning and agent startup.

The metric is emitted when the agent reports ready/error/timeout via the
lifecycle API, ensuring each build is counted exactly once per replica.

coderd/database/queries/workspacebuilds.sql

@@ -243,3 +243,31 @@ SET
 	has_external_agent = @has_external_agent,
 	updated_at = @updated_at::timestamptz
 WHERE id = @id::uuid;
+
+-- name: GetWorkspaceBuildMetricsByResourceID :one
+-- Returns build metadata for e2e workspace build duration metrics.
+-- Also checks if all agents are ready and returns the worst status.
+SELECT
+    wb.created_at,
+    wb.transition,
+    t.name AS template_name,
+    o.name AS organization_name,
+    (w.owner_id = 'c42fdf75-3097-471c-8c33-fb52454d81c0') AS is_prebuild,
+    -- All agents must have ready_at set (terminal startup state)
+    COUNT(*) FILTER (WHERE wa.ready_at IS NULL) = 0 AS all_agents_ready,
+    -- Latest ready_at across all agents (for duration calculation)
+	MAX(wa.ready_at)::timestamptz AS last_agent_ready_at,
+    -- Worst status: error > timeout > ready
+    CASE
+        WHEN bool_or(wa.lifecycle_state = 'start_error') THEN 'error'
+        WHEN bool_or(wa.lifecycle_state = 'start_timeout') THEN 'timeout'
+        ELSE 'success'
+    END AS worst_status
+FROM workspace_builds wb
+JOIN workspaces w ON wb.workspace_id = w.id
+JOIN templates t ON w.template_id = t.id
+JOIN organizations o ON t.organization_id = o.id
+JOIN workspace_resources wr ON wr.job_id = wb.job_id
+JOIN workspace_agents wa ON wa.resource_id = wr.id
+WHERE wb.job_id = (SELECT job_id FROM workspace_resources WHERE workspace_resources.id = $1)
+GROUP BY wb.created_at, wb.transition, t.name, o.name, w.owner_id;