[util_rand_resp] Update reference style across lecture and correct typos (#621)

* updates

* update typos

* move reference below the figure

* fix minor error

* remove references in the subtitles

* update one-sentence rule

* updates

* updates

* Address review: restore Chaudhuri-Mukerjee figure and fix style issues

The last figure had been replaced by a copy of the Lanke figure, dropping
the convex truth border that the Chaudhuri-Mukerjee section is about and
orphaning f(x). Restore it, keeping only the intended fix (legend label
Z -> Q, matching the prose).

Other fixes:

- restore title case in the lecture title (style guide: title case for
  lecture titles, sentence case for section headings)
- split the nested prf:assumption into two directives, so the numbering
  doesn't collide with the directive's own "Assumption 1" label
- reword the three {cite:t} conversions that lost a possessive
  ("Warner (1965) original model" -> "the original model of ...")
- convert the remaining Anderson and Warner citations to {cite:t}
- shorten figure captions to the 5-6 word guideline
- fix duplicate {eq} reference (nine-a -> nine-b)
- undo code wrapping of lines already under 79 characters and replace
  backslash continuations
- reference fig-truth-borders with numref; restore the concave/convex
  sentence to its bullet; strip trailing whitespace

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

* Bring figures into style-guide compliance

- drop figsize=(12, 10) from all five figures and use the default size
- convert plt.* to the fig, ax = plt.subplots() / ax.* pattern
- use lw=2 on line charts, and lw instead of linewidth
- set in-figure text in roman lower case ("truth telling", not italic
  "Truth Telling") at the default size, and drop legend fontsize='large'
- lower-case the legend labels ("truth border")
- label the iso-variance family once instead of V1..V9, which cuts the
  legend from twelve entries to four and lets the existing "high
  variance" / "low variance" annotations carry the ordering; the prose
  bullet that referred to V1..V9 is reworded to match
- shorten the truth-border legend labels, writing p for Pr(A|r_i), with
  the shorthand introduced in the preceding sentence
- replace the Iso_Variance class with a plot_iso_variance_curves
  function (the class held only two attributes and one plotting method)
- vectorize f() with np.where so the Chaudhuri-Mukerjee truth border is
  computed in one place instead of being repeated inline

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

* Normalize jupytext metadata and blank lines

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: John Stachurski <john.stachurski@gmail.com>
Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: 3 people