Add exponents & roots bundle (quant/arithmetic)

[DMDaudio]

What does this PR add or change?

Adds coverage for the previously-empty quant / arithmetic / exponents-roots subtopic — one lesson plus 7 original problem-solving questions with an easy→hard progression.

Lesson (quant-arithmetic-exponents-roots): exponent laws (product/quotient/power-of-a-power), zero and negative exponents, fractional exponents as roots, simplifying and combining radicals, and solving exponential equations via a common base — with worked examples, a common-traps list, and key takeaways.

Questions (quant-arithmetic-exponents-roots-0017–0023):

ID	Difficulty	Focus
0017	easy	combining product/quotient rules (spot the lone 5^1)
0018	easy	zero and negative exponents
0019	medium	simplifying and adding radicals
0020	medium	fractional exponent 27^(2/3)
0021	medium	splitting 2^(x+3) with a given 2^x
0022	hard	common-base equation 3^(x+1) = 27^2
0023	hard	quotient of roots minus a square root

Every question has a full worked explanation, two hints, and distractors each keyed to a specific common error (e.g. adding under the radical, treating a negative exponent as a negative number, power-tower misreads).

docs/data/content.json regenerated with node scripts/build.mjs — 39 questions / 9 lessons, zero warnings.

Type of change

• New question(s)
• New lesson(s)
• Fix to existing content (answer / explanation / tag)
• Tooling / docs / schema

Author checklist

• This is my own original work — not copied or paraphrased from any real GMAT question or prep material.
• Front-matter follows CONTENT_SCHEMA.md (id matches the filename; topic/subtopic exist in curriculum.md).
• I solved every question myself and confirmed exactly one answer choice is correct.
• Each explanation would help someone who got the question wrong, and names the trap where relevant.
• status is in-review. I did not set my own content to verified.

For reviewers

• I solved the question(s) without reading the keyed answer first and got the same answer.
• Exactly one choice is correct; distractors are plausible.
• Explanation and tags (section / topic / difficulty) are accurate.
• If approving: bumped status to verified and added my handle to reviewers.

🤖 Generated with Claude Code

https://claude.ai/code/session_01MDSYiSKES81qTDhpYqMemD

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