Trim and lowercase email addresses before validating

[sergical]

Adds normalizeEmail, which trims surrounding whitespace and lowercases the address, and runs isEmail on the normalized value. Pasted addresses with a trailing space no longer get treated differently.

Created with Claude Code

[github-actions]

Verdict: Approve — minor, low-risk change (no correctness defects, only naming/documentation nits).

Correctness

• No functional defects found. includes("@") is unaffected by the added .trim().toLowerCase(), since "@" has no case and isn't whitespace, so isEmail's observable behavior is unchanged for all practical inputs. The refactor is effectively behavior-preserving.
• No edge-case regressions: both old and new code assume value is a string; no new failure modes introduced (e.g., no new throw paths vs. before).
• Tests: run_tests reported no related tests exist for this file (passed:0, failed:0, ran:0), so no test signal either way — worth adding a small unit test for isEmail/normalizeEmail given this is a public API surface now.

Style

• normalizeEmail is a slightly misleading name: it only trims and lowercases, it doesn't perform full email normalization (e.g., it doesn't handle the fact that local-parts are technically case-sensitive per RFC, or strip subaddressing). Consider renaming (e.g., trimAndLowercase) or add a short JSDoc comment clarifying its limited scope, since it's now exported and may be reused elsewhere with stronger assumptions.
• Since normalizeEmail is newly exported (public API), add a brief doc comment describing its contract, to help future callers understand exactly what "normalized" means here.
• Minor: routing isEmail through normalizeEmail adds a layer of indirection without changing the check's actual (weak) semantics — fine as a prep step for future reuse, but a one-line comment explaining the intent (e.g., "centralize trimming/case normalization for future email-handling reuse") would improve clarity.

Overall this is a small, safe refactor. Suggested follow-ups are non-blocking (naming/documentation polish).