Exercise 1: Why fmt -check and validate Run Before plan, and What Each Catches — Possible Solution
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Both `fmt -check` and `validate` are LOCAL, CHEAP checks -- neither
needs to talk to a real cloud provider or compute an actual
infrastructure diff. `plan`, by contrast, is comparatively expensive:
it refreshes real state against real infrastructure (Chapter 5's
three-way comparison) and can take real time against a large
configuration. Running the cheap checks first means a pipeline fails
FAST on a trivial mistake -- a badly formatted file or a syntax error
-- without ever spending the time (and, for some providers, real API
calls) needed to compute a full plan. This is the same "fail fast"
logic behind ordering any CI pipeline's cheapest checks earliest.

What each one specifically catches, and why neither substitutes for
the other:

- `terraform fmt -check` catches STYLE inconsistency only -- inconsistent
  indentation, spacing, alignment. It has no awareness of whether the
  configuration is even valid HCL; a file could be perfectly formatted
  and still reference an undefined variable.

- `terraform validate` catches SYNTAX and TYPE errors -- malformed HCL,
  a variable referenced that was never declared, an argument of the
  wrong type -- but does not care at all about formatting style, and
  critically, it doesn't touch real infrastructure or compute an actual
  plan; it only checks that the configuration is internally
  well-formed.

Neither one can catch what `plan` catches (an actual, real diff against
live infrastructure) -- they're deliberately narrower, cheaper filters
that catch different, non-overlapping classes of trivial mistakes
before the pipeline pays for a full plan.

WHY THIS WORKS AS AN ANSWER
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This explains the fail-fast/cost-ordering reasoning for running cheap
checks first, and clearly separates what fmt (style) vs. validate
(syntax/types) each catches, showing they check genuinely different,
non-redundant things rather than treating them as interchangeable.