refactor(learn): drop em dashes from the course content

[joaopcm]

Em dashes are one of the more reliable AI-writing tells, and the course content had 175 of them across the nine units and their quizzes. This removes all of them from reader-facing text.

Scope

In: the nine unit.mdx files, every quiz.ts prompt and explanation, and the running prose in page.tsx, setup-note.tsx, and progress-note.tsx.

Out, deliberately:

• Code comments. Not something a learner reads, and this repo's own comment style already reaches for the dash in asides throughout the codebase — changing that here would be inconsistent with everywhere else.
• The Label — value UI convention: Unit 00 — locked (gate.tsx), Run this — auth (lookup.tsx), Next — {title} (quiz.tsx), and the same shape in spine.tsx, exam.tsx, start-link.tsx. That's a deliberate, consistent design pattern for compact status strings, not prose with an AI tic. Changing it would be a design decision, not a writing fix.
• lookups.spec.ts's own explanatory comments, same reasoning as the first point.

How, not just what

No mechanical find-and-replace. A uniform substitution is its own tell — real writing doesn't reach for the same punctuation mark every time. Each instance was read in its sentence and repunctuated for what that sentence is actually doing:

• Colon where the second clause explains or elaborates the first — the most common case by far
• Comma where a conjunction (and, so, but, which) already carried the logical relation and the dash was doing nothing
• Parentheses where the text was a genuine aside — usually a paired em dash wrapping an example or a gloss
• Period, splitting into two sentences, where the clauses were fully independent

Example of the range, from unit 6:

- deliberately — a verify that consulted one resolver and a sweep that
+ deliberately: a verify that consulted one resolver and a sweep that

- both servers are listed in the delegation — so a resolver
+ both servers are listed in the delegation, so a resolver

- getting the once-per-episode property out of it — rather than out of a
- separate suppression rule somewhere else — is why there is nothing here
+ getting the once-per-episode property out of it (rather than out of a
+ separate suppression rule somewhere else) is why there is nothing here

Three different fixes for three different sentences, because they needed different things.

What I checked

• grep -rc '—' apps/learn/src/content --include=*.mdx → 0
• grep -rc '—' apps/learn/src/content --include=*.ts → 0 outside lookups.spec.ts comments
• Read every rewritten sentence back for flow, not just for the absence of the character
• curriculum.spec.ts reads unit.mdx headings off disk and matches them against the declared curriculum; no heading text was touched, so that guard still holds
• pnpm --filter @propgate/learn build and the full pnpm --filter @propgate/learn vitest run (70/70)
• Workspace-wide pnpm lint, pnpm check, pnpm test --force — 12/12 tasks, nothing cached

134 changes across 19 files, all 1:1 line replacements — no prose restructuring beyond the punctuation itself, no new claims, nothing added or removed in substance.

[greptile-apps]

Your trial has ended. Reactivate Greptile to resume code reviews.