[vEnhance]

Closes #61.

Proofread src/sol-foxtrot.typ and found a handful of small errors, plus one dangling cross-reference:

• exer-lattice-saddle: the boxed identity cos((x-y)pi) - cos((x+y)pi) = sin(pi x) sin(pi y) was missing a factor of 2 (the correct product-to-sum identity is cos(A-B) - cos(A+B) = 2 sin A sin B). Fixed by dividing the cosine difference by 2.
• exer-opt-lm-sin: the boundary case x = 0 gives sin(y) = 1, whose solutions are y = pi/2 + 2 pi k (pi/2, 5pi/2, 9pi/2, ...), not y = pi, 3pi, 5pi, ... as previously written; same issue (and same fix) for the symmetric y = 0 case. Updated the stated bound from x+y >= pi to the correct x+y >= pi/2 (the conclusion is unchanged, since pi/2 > pi/3).
• exer-mt2p4: the prose bullet stated A = -pi^2 for odd x and A = pi^2 for even x, which is backwards — it contradicts the table immediately below it (and the correct sign is confirmed by the later "critical points of a(x) = cos(pi x)" discussion). Swapped the parities to match.
• exer-mt2p5: (x,y,z) = (10/l, 20/3, 20/3) had a typo, l instead of 3.
• Grammar/clarity fixes in the exer-every-saddle solution: "We will prove that the following result" → "We will prove the following result", and "every point of f will be both a local minimum or local maximum" → "... both a local minimum and a local maximum".
• The tangent-plane solution (exer-mt2p6) referenced the "buy two get one free" result with a dangling, unfinished sentence ("result from\nwe just need..."). Added a label <sec-detect-basis> to the corresponding recipe section in src/basis.typ and completed the cross-reference.

No large mathematical errors were found; all the issues above were minor (sign/factor slips, a stray typo, or unfinished prose).

Test plan

• Installed typst + the @local/evan:1.0.0 package and all required @preview deps, then ran typst compile lamv.typ end-to-end (with placeholder SVGs standing in for Asymptote figures, since asy isn't available in this environment) — compiles cleanly with no errors, confirming the new @sec-detect-basis reference resolves and no syntax was broken.

🤖 Generated with Claude Code

https://claude.ai/code/session_01EH8uPmHRTBg3EmEXmR7225

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