feat(makefile): add deps, diff, lint targets and fzf-picker fallback

Ports useful quality-of-life targets from DeepSat's coding-rulesets
Makefile, adapted to this repo's two-scope (global + per-project)
structure.

New targets:
  make deps                       Install claude, jq, fzf, ripgrep,
                                  emacs via brew/apt/pacman. Idempotent
                                  (skips already-present tools). For
                                  new machines and VMs.

  make diff LANG=<lang> [PROJECT=<path>]
                                  Show unified diff between repo source
                                  and installed copies in a target
                                  project. CLAUDE.md excluded (seed-
                                  only, diverges by design).

  make lint                       Validate ruleset structure: top-level
                                  headings, 'Applies to:' headers on
                                  rule files, shebangs and exec bits on
                                  hook scripts.

Infrastructure:
  - Help migrated to awk-parsed ##@/## pattern; new targets document
    themselves via a single trailing `## ...` comment.
  - fzf-picker fallback: if PROJECT= is unset, install-lang and diff
    launch fzf over local .git dirs under $HOME. Keeps PROJECT=<path>
    for scripts/automation; only interactive users hit fzf.

  scripts/diff-lang.sh  Walks the file list the installer would copy,
                        diffs each against the target.
  scripts/lint.sh       Standalone ruleset structure validator.

0 files changed, 0 insertions, 0 deletions