fix(scripts): make install.sh / build.sh work on stock macOS

Stock macOS ships bash 3.2 (frozen 2007 due to GPLv3) and BSD find.
Both scripts used `mapfile` (bash 4+) and `find -printf` (GNU only),
so a fresh Mac user running `bash scripts/install.sh` died on line 11
before copying anything. Replace with a portable shell glob — same
sort order, no `find` dependency, works on bash 3.2 and 4+.

Verified on git-bash: 16 skills discovered, install dry-run copies all,
`build.sh` produces a valid archive.

See .wiki/concepts/install-portability.md for the full gotcha.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.wiki/log.md

@@ -27,3 +27,4 @@ Parseable: `grep "^## \[" .wiki/log.md | tail -20`.
 ## [2026-04-28] refactor | tasks split — `task-status-wiki` renamed to `using-tasks` (policy); new `setup-tasks` skill owns greenfield + interactive migration (no auto-parsing of old flat STATUS.md); `project-bootstrap` Step 4 delegates
 ## [2026-04-28] refactor | this repo's `.tasks/` migrated to canonical layout — flat `## Done`/`## Backlog` replaced by emoji-status board (7 ⚪ Ready blocks); historical Done entries dropped (preserved in git log); `.bak` ignored via .gitignore
 ## [2026-04-28] cleanup | removed stale `~/.claude/skills/{wiki-maintainer,task-status-wiki}/` installs (replaced by `using-wiki`/`using-tasks`); 16 skills installed, no duplicates; context7 plugin (mcp__plugin_context7_context7__*) confirmed live after restart
+## [2026-04-28] decision | install-portability — `install.sh`/`build.sh` patched to drop `mapfile`+`find -printf`; stock macOS (bash 3.2 + BSD find) now works; verified on git-bash (16 skills discovered, sorted, installed; build.sh produces archive)