Bump Koda's maxBootstrapChars 20000 → 28000

Koda flagged (Apr 23) that AGENTS.md was truncating to 329/9387 chars every session and the daily memory file was being skipped entirely. 6+ sessions compounding.

Fix landed in koda-runtime/config.json:73. Picks up on Koda’s next restart. Ada framed it as “good data either way” — if 28K holds, great; if not, we learn the file set has grown past that too.

Also updated config.example.json so new runtimes get 28000 as the default from the start. Commit 6929542 pushed.