[Cross-cutting] Remove marketing language, filler phrases and fake case studies #1901

Problem

A pervasive tone issue across every part of the book: marketing language, clichés, "transformation journey" vocabulary, and fabricated case studies without names or figures.

Remove these words and phrases where they appear without substance

• "comprehensive", "sophisticated", "mature", "backbone", "modern"
• "pays dividends", "competitive advantage", "strategic imperative"
• "transformation journey", "mindset", "culture eats strategy"
• "in this chapter we will..." / "this chapter explores..." (filler reformulations of the heading)
• "European organisations face unique challenges..." as an opening
• "The diagram illustrates..." when the text paraphrases the image instead of adding information

Fake case studies to remove or name

• 19_management_as_code.md:286–287: "Consider a global software company operating in regulated financial markets..."
• 04_adr.md:234–242: "This workflow prevented significant disruption during a recent platform rotation..." (vague anecdote with no figures)
• 26a_prerequisites_for_aac.md:100–104: "A multinational financial services group offers a useful illustration..."
• 21_digitalisation.md:66–78 and 194–213: Spotify/Stripe/Netflix/Capital One with unsourced figures, and duplicated within the same chapter
• 24_best_practices.md:3: "...lessons learned from teams operating at scale across finance, public services, healthcare, media..." — none of these "teams" are ever named

Unsourced figures to cite or remove

• 21_digitalisation.md:38: "£500 billion in digital transformation initiatives" — no source
• 21_digitalisation.md:44: "reduces manual effort by up to 70%" — no source
• 21_digitalisation.md:255–263: GE/Siemens/ABB anecdotes without a source

Expected saving

~100 lines scattered throughout + a significant improvement in tone.

Source

Hard critical review of Parts A–H. See CUT_PROPOSAL.md.