Exercise 2: Two Steps, Multiple Chapters Each — Possible Solution
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EXAMPLE 1 — STEP 1, SCANNING
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Scanning depends on at least two chapters working together. Chapter 4
supplies the actual barcode via a client-side hook with no knowledge of
any backend at all. Chapter 3 supplies the route that hook's own
callback calls - the lookup endpoint that checks BarcodeCache and
falls back to Open Food Facts. Neither chapter alone produces a working
scan: Chapter 4's hook with no route to call would decode a barcode
and go nowhere, and Chapter 3's route with no way to trigger it from a
camera would never receive a barcode to look up in the first place.

EXAMPLE 2 — STEP 4, SEARCHING
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Searching depends on at least three chapters together. Chapter 7
supplies the debounce hook and the contains-based search route itself.
But that route only matches case-insensitively because of a migration
Chapter 7 itself generated and hand-edited to add COLLATE NOCASE to the
name column - without that specific fix, applied as its own real step,
the same route code would return zero results for "yog" against an
item named "Yogurt." The search also implicitly depends on Chapter 2's
own original schema, since name has to exist as a column at all before
any collation could be applied to it.

WHY THIS WORKS AS AN ANSWER
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Both examples correctly identify at least two genuinely separate
pieces of functionality (a frontend hook and a backend route in the
first case; a query, its own supporting migration, and the original
schema in the second) rather than attributing the whole step to a
single chapter, and each explains concretely what would break if one
of the contributing chapters' own work were missing.