feat(rules): rules/ directory symlinked into ~/.claude like the other dirs

Claude Code loads modular rule files from ~/.claude/rules/ (user scope,
recursive, markdown, optional paths: frontmatter for lazy path-scoped
loading — stable, symlink-supported). The repo had no rules/ at all, so
the ctx7 setup had created ~/.claude/rules as a REAL directory outside
version control — invisible to the repo, unreproducible on a new machine.

- rules/README.md — doctrine: one rule per file; paths:-scoped extraction
  is the token win, always-on doctrine stays in CLAUDE.md
- link.sh — rules added to the symlinked-dirs loop
- .gitignore — rules/context7.md ignored (machine-owned: `ctx7 setup`
  (re)writes it, same treatment as skills/find-docs/)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XpphkdTosUzokBDNG7PToS

.gitignore

@@ -74,6 +74,10 @@ skills/find-skills
 # this repo's skills/). ctx7-managed and re-created on demand — not vendored here.
 skills/find-docs/
 
+# Context7 rule — (re)written by the same `ctx7 setup` into ~/.claude/rules (a
+# symlink to this repo's rules/). ctx7-managed — not vendored here.
+rules/context7.md
+
 # Staging area used by lib/toggle-external.sh when disabling a tool
 skills-disabled/