fix: remove unwrap in schema.rs header alias builder + complete PR #2 code review

[Copilot]

PR #2 had an incomplete code review — all 7 originally identified issues (RI-01 through RI-07) were already resolved in the merged code, but the review was never finalized and one additional issue was left unfixed.

Changes

• src/schema.rs — build_header_aliases: removed .unwrap() on Vec<char> (logically safe but convention violation). Replaced with a panic-free let chain using chars().next() / chars().next_back(), also eliminating the unnecessary heap allocation:

// before
let chars: Vec<char> = sanitized.chars().collect();
let first = chars.first().copied().unwrap();
let last = chars.last().copied().unwrap_or(first);
try_insert(&format!("{}{}", first, last));

// after
if sanitized.len() >= 2
    && let (Some(first), Some(last)) =
        (sanitized.chars().next(), sanitized.chars().next_back())
{
    try_insert(&format!("{first}{last}"));
}

• Review tracking — updated .copilot-tracking/pr/review/001-baseline-sdd-spec/ to mark the review complete, record the fix, and log the remaining non-blocking item (NEW-02: 216 public items missing /// Rustdoc — recommended for a follow-up PR).

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[Copilot]

Pull request overview

This PR removes the last unwrap() in src/schema.rs’s build_header_aliases() shorthand builder (avoiding both panics and an unnecessary Vec<char> allocation) and updates Copilot review-tracking artifacts intended to close out the previously incomplete review for PR #2.

Changes:

• Refactor build_header_aliases() to derive the first/last character shorthand without allocating and without unwrap().
• Mark the PR #2 review as complete and record quality-gate status in the Copilot tracking review doc.
• Add a review handoff document under .copilot-tracking/ (but it currently contains outdated guidance about the already-fixed unwrap()).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
src/schema.rs	Removes unwrap() and avoids Vec<char> allocation in header alias shorthand generation
.copilot-tracking/pr/review/001-baseline-sdd-spec/in-progress-review.md	Updates review status/notes and quality gate results, but still describes NEW-01 as if it’s unresolved
.copilot-tracking/pr/review/001-baseline-sdd-spec/handoff.md	Adds a handoff doc, but includes an outdated “ready for submission” comment about an unwrap() that no longer exists