fix(phase): update overview bullet checkbox on phase complete (#1998) (#2000)

cmdPhaseComplete used replaceInCurrentMilestone() to update the overview
bullet checkbox (- [ ] → - [x]), but that function scopes replacements
to content after the last </details> tag. The current milestone's
overview bullets appear before any <details> blocks, so the replacement
never matched.

Switch to direct .replace() which correctly finds and updates the first
matching unchecked checkbox. This is safe because unchecked checkboxes
([ ]) only exist in the current milestone — archived phases have [x].

Closes #1998

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

get-shit-done/bin/lib/phase.cjs

@@ -712,7 +712,7 @@ function cmdPhaseComplete(cwd, phaseNum, raw) {
         `(-\\s*\\[)[ ](\\]\\s*.*Phase\\s+${escapeRegex(phaseNum)}[:\\s][^\\n]*)`,
         'i'
       );
-      roadmapContent = replaceInCurrentMilestone(roadmapContent, checkboxPattern, `$1x$2 (completed ${today})`);
+      roadmapContent = roadmapContent.replace(checkboxPattern, `$1x$2 (completed ${today})`);
 
       // Progress table: update Status to Complete, add date (handles 4 or 5 column tables)
       const phaseEscaped = escapeRegex(phaseNum);