How can I programmatically extract the text content from a Notebook's cell definition?

Question

Given the Notebook cell definition below from the Wolfram Function Repository as an example:

Cell[BoxData[{
 RowBox[{"Clear", "[", "Bob", "]"}], "\[IndentingNewLine]", 
 RowBox[{
  RowBox[{
   RowBox[{"Options", "[", "Bob", "]"}], "=", 
   RowBox[{"{", 
    RowBox[{"UpdateInterval", "\[Rule]", "0.05"}], "}"}]}], ";"}], "\n", 
 RowBox[{
  RowBox[{"Bob", "[", 
   RowBox[{"expr_", ",", 
    RowBox[{"opts", ":", 
     RowBox[{"OptionsPattern", "[", "]"}]}]}], "]"}], ":=", 
  RowBox[{"Bob", "[", 
   RowBox[{"expr", ",", "1", ",", "1", ",", "opts"}], "]"}]}], "\n", 
 RowBox[{See
  RowBox[{"Bob", "[", 
   RowBox[{"expr_", ",", "rate_", ",", 
    RowBox[{"opts", ":", 
     RowBox[{"OptionsPattern", "[", "]"}]}]}], "]"}], ":=", 
  RowBox[{"Bob", "[", 
   RowBox[{"expr", ",", "rate", ",", "1", ",", "opts"}], "]"}]}], "\n", 
 RowBox[{
  RowBox[{"Bob", "[", 
   RowBox[{"expr_", ",", "Automatic", ",", "rest___"}], "]"}], ":=", 
  RowBox[{"Bob", "[", 
   RowBox[{"expr", ",", "1", ",", "rest"}], "]"}]}], "\n", 
 RowBox[{"Bob", "/:", 
  RowBox[{"MakeBoxes", "[", 
   RowBox[{
    RowBox[{
     RowBox[{"HoldPattern", "[", "Bob", "]"}], "[", 
     RowBox[{"expr_", ",", "rate_", ",", "magnitude_", ",", 
      RowBox[{"OptionsPattern", "[", "Bob", "]"}]}], "]"}], ",", "form_"}], 
   "]"}], ":=", 
  RowBox[{"AdjustmentBox", "[", 
   RowBox[{
    RowBox[{"ToBoxes", "[", 
     RowBox[{"expr", ",", "form"}], "]"}], ",", 
    RowBox[{"BoxBaselineShift", "\[Rule]", 
     RowBox[{"Dynamic", "[", 
      RowBox[{"Refresh", "[", 
       RowBox[{
        RowBox[{"magnitude", "*", 
         RowBox[{"Sin", "[", 
          RowBox[{
           RowBox[{"N", "@", 
            RowBox[{"AbsoluteTime", "[", "]"}]}], "*", "rate"}], "]"}]}], ",", 
        RowBox[{"UpdateInterval", "\[Rule]", 
         RowBox[{"OptionValue", "[", 
          RowBox[{"Bob", ",", "UpdateInterval"}], "]"}]}]}], "]"}], "]"}]}]}],
    "]"}]}], "\[IndentingNewLine]", 
 RowBox[{
  RowBox[{"ResourceFunction", "[", "\"\<FormatAsResourceFunction\>\"", "]"}], 
  "[", "Bob", "]"}]}], "Input",
 CellEventActions->{Inherited, {"KeyDown", "\t"} :> Replace[SelectionMove[
       SelectedNotebook[], After, Cell]; NotebookFind[
       SelectedNotebook[], "TabNext", Next, CellTags, AutoScroll -> True, 
       WrapAround -> True], Blank[NotebookSelection] :> SelectionMove[
       SelectedNotebook[], All, CellContents, AutoScroll -> True]], 
   PassEventsDown -> False, PassEventsUp -> False},
 CellChangeTimes->{{3.7686653112660103`*^9, 3.768665313802607*^9}, {
  3.76866535043878*^9, 3.76866544731925*^9}, {3.768665643440073*^9, 
  3.76866568116868*^9}},
 CellTags->"TabNext",
 CellLabel->"In[17]:=",
 CellID->778396829]
}, Open  ]],

How can I programmatically extract the text content from a Notebook's cell definition?

Few remarks:

• The goal is to write a script part of a toolchain to convert from notebooks to a text format more suitable for integration with my website engine. I'm primarily concerned with cells containing plain text or Wolfram Language source code.
• I initially considered extracting the cell's content as a string. But extracting it as an InputForm might be more suitable.
• By programmatically, I understand the conversion could run unattended on a developer kernel, without requiring a front-end and without user interaction. For example, most answers in a previous question (How do I extract the contents of a selected cell as plain text?) are using the clipboard, a solution that shouldn't¹ be suitable for my needs.

---

_{¹ As far as I understand it at least}