#5 Commits pages + per-commit diffs + wiki

Context: "Entire state" requires commit history with diffs + wiki. Depends on gitx (#3). Tasks:

• /commits.html: latest 100 (flag --max-log), short sha, subject, author, date, link to detail.
• /commit/<sha>.html: full message (escaped) + unified diff as escaped <pre> (binary files noted, huge diffs truncated with note + full diff downloadable as raw? keep: truncate at 2000 lines with marker).
• /wiki/: index (tree + first-H1 titles, dirs skipped per f0rge rules: symlinks skipped, >256KiB skipped) + page render; missing page links 404-style placeholder at build (skip + warn). Success rubric:
• 100-commit fixture renders list in order; detail diff contains expected hunks, escaped.
• Wiki index titles match first-H1 rule; symlink + oversize fixtures skipped with stderr warn, build still 0. Swarm: Owl. Branch m2/commits-wiki.