docs: rewrite the README for someone meeting the language

The README opened with three restatements of "no C", then a limitations table,
then a repo-layout map, and closed with Chrono Rift's keybindings — P2/Mage
`I`/`K` select, `J` confirm — which is a game manual, not a language README. It
never showed the language itself.

It now leads with what Ludic is, a compiling code sample, how to build, what the
language offers, and an honest status. The layout table is contributor material
and CONTRIBUTING already covers that ground.

Two things were not merely stylistic:

- Nine links pointed at wiki pages that no longer exist.
- "Language at a glance" advertised `system` with `reads`/`writes`, plus
  `requires`/`ensures`. None of those are keywords — the grammar has `handler`,
  and `System.*` is a namespace. That bullet described a vocabulary retired
  several releases ago.

The sample is verified to compile, every internal link resolves, and every
command named is one `x help` actually offers.

Also makes commit-lint survive a force-push: it linted `event.before..sha`
without checking that `before` still resolves, so rewriting or gc'ing that
commit failed the job with "Invalid revision range" on a push whose messages
were all valid.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.forgejo/workflows/commit-lint.yml

@@ -35,10 +35,15 @@ jobs:
           #  - pull_request: base branch .. this commit
           #  - push:         the pushed range (event.before .. this commit)
           #  - new branch / unknown: just the tip commit
+          # `event.before` is only usable if it still resolves: a force-push
+          # rewrites (and a gc can remove) the commit it names, which made this
+          # job fail with "Invalid revision range" on an otherwise clean push.
+          # Fall back to the tip commit in that case.
           if [ -n "${BASE:-}" ]; then
             git fetch --quiet origin "${BASE}" 2>/dev/null || true
             RANGE="origin/${BASE}..${GITHUB_SHA}"
-          elif [ -n "${BEFORE:-}" ] && ! printf '%s' "$BEFORE" | grep -qE '^0+$'; then
+          elif [ -n "${BEFORE:-}" ] && ! printf '%s' "$BEFORE" | grep -qE '^0+$' \
+               && git cat-file -e "${BEFORE}^{commit}" 2>/dev/null; then
             RANGE="${BEFORE}..${GITHUB_SHA}"
           else
             RANGE="${GITHUB_SHA}~1..${GITHUB_SHA}"