fix(file-search): rank exact-term edit target case-insensitively

[thejesh23]

What

Fixes edit-target ranking in performSearch: an exact search-term hit was sometimes left at medium confidence (and outranked by an unrelated line) because the confidence check re-tested the term case-sensitively, while the term itself is matched case-insensitively.

Fixes #217

Root cause

lib/file-search-executor.ts matches terms case-insensitively:

if (line.toLowerCase().includes(term.toLowerCase())) { ... matchedTerm = term; }

but the confidence check re-tested case-sensitively:

if (matchedTerm && line.includes(matchedTerm)) { confidence = 'high'; }
else if (line.includes('function') || line.includes('export') || line.includes('return')) { confidence = 'high'; }

On a casing mismatch the exact-match branch is skipped, so the real target stays medium, while an unrelated line containing return/export/function is promoted to high and sorts above it — pointing selectTargetFile at the wrong line.

Fix

-if (matchedTerm && line.includes(matchedTerm)) {
+if (matchedTerm && line.toLowerCase().includes(matchedTerm.toLowerCase())) {
   confidence = 'high';

Verification

searchTerms: ["Sign Up"] against:

<button>sign up</button>       // the real edit target
// return to sign up page       // unrelated comment

Line	Before	After
<button>sign up</button>	medium	high
// return to sign up page	high (via return)	high

The real target is now correctly ranked high instead of being downgraded below the comment.