Exercise 1: What "No Changes" Confirms, Connected to Chapter 1's Idempotency Exercise — Possible Solution
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"No changes" is Terraform's plan output stating that, after comparing
the configuration's declared desired state against the ACTUAL current
state (the real hello.txt file now sitting on disk, tracked via
Terraform's own state), the two already match exactly -- there is
nothing left for Terraform to create, update, or destroy.

This is a direct, concrete demonstration of Chapter 1 Exercise 1's own
answer: a declarative tool avoids the "run it twice and it breaks"
problem specifically BECAUSE it compares desired state against actual
state before acting, rather than blindly re-executing a fixed sequence
of steps. Chapter 1 explained this in the abstract; this chapter proves
it in practice -- running `apply` a first time created the file
(desired state didn't match actual state, so Terraform acted), and
running `plan` again immediately afterward, with nothing having
changed, produces genuinely zero planned actions, because desired state
and actual state are now identical. Re-running the same configuration
any further number of times would produce the exact same "No changes"
result every time, which is the idempotency property named directly in
that exercise's own solution.

WHY THIS WORKS AS AN ANSWER
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This explicitly traces the "No changes" output back to the specific
mechanism (desired-vs-actual-state comparison) Chapter 1 Exercise 1
already explained in the abstract, showing this chapter's real example
as concrete proof of that same abstract claim rather than treating them
as two unrelated facts.