Improve Chapter 01 notation conventions lesson

[jules-tth]

Scope

• Replaces the generic 1.05 notation page with a practical operator lesson.
• Covers prompts, literal text, placeholders, manual-page syntax markers, files/program notation, shell quoting, and safe copy/paste habits.
• Adds hands-on practice and check-your-understanding questions focused on reproducible command examples.

Verification

• python -m pip install -r requirements.txt could not run because python is not on PATH.
• python3 -m pip install -r requirements.txt passed.
• python3 -m mkdocs build --strict passed.
• make build passed.
• git diff --check passed.
• find docs -type f -name "*.md" -size 0 -print returned no files.

Reviewer

Requested review from @bdorlus via gh pr create --reviewer.

Duplicate-prevention

Open PR check before creation found no open PR from jules-tth touching docs/lessons/01_where_to_start/1.05_notation_and_typographical_conventions.md.

[jules-tth]

Reviewer assignment to bdorlus failed during PR creation: GraphQL: jules-tth does not have the correct permissions to execute RequestReviewsByLogin (requestReviewsByLogin)