chore(config): pre-push — fall back to origin/main on first push

When a new branch is pushed for the first time, origin/<branch> does
not yet exist, so the pre-push hook was falling through to treating
every directory as changed. On a wiki-only branch this meant running
Godot headless parse, cargo fmt + clippy, ruff, and validating all
2762 repo-wide JSON files — tens of seconds of churn against a diff
that had no client/server/tooling/JSON content.

Fix: try origin/<branch> first, fall back to origin/main before
giving up. The JSON validation block now uses the same REMOTE_REF
the directory-change detection settled on, so both code paths stay
consistent.

Scope note: this is CI/tooling infrastructure, not copy-team scope,
but surfaced as part of reviewing the slow push on sprint-37/copy.
Bundling here rather than a separate branch at Jeroen's direction.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.config/hooks/pre-push

@@ -9,14 +9,27 @@ ERRORS=0
 echo "pre-push: running lint checks..."
 
 # --- Detect which directories have changes vs remote ---
+# Prefer origin/<branch> as the baseline (what the remote already has),
+# but fall back to origin/main for first-push of a new branch — otherwise
+# every check runs against nothing and the hook treats the whole repo as
+# changed, spending tens of seconds on linters and JSON validation that
+# have no diff to cover (e.g. pushing a wiki-only branch rebuilds GDScript
+# and runs clippy + ruff + validates all 2762 JSON files).
 BRANCH=$(git branch --show-current)
-REMOTE_REF="origin/$BRANCH"
-if git rev-parse --verify "$REMOTE_REF" >/dev/null 2>&1; then
+if git rev-parse --verify "origin/$BRANCH" >/dev/null 2>&1; then
+    REMOTE_REF="origin/$BRANCH"
+elif git rev-parse --verify "origin/main" >/dev/null 2>&1; then
+    REMOTE_REF="origin/main"
+else
+    REMOTE_REF=""
+fi
+
+if [ -n "$REMOTE_REF" ]; then
     CLIENT_CHANGED=$(git diff --name-only "$REMOTE_REF"..HEAD -- client/ 2>/dev/null | wc -l)
     SERVER_CHANGED=$(git diff --name-only "$REMOTE_REF"..HEAD -- server/ 2>/dev/null | wc -l)
     TOOLING_CHANGED=$(git diff --name-only "$REMOTE_REF"..HEAD -- tooling/ pyproject.toml 2>/dev/null | wc -l)
 else
-    # New branch or no remote ref — fall through to directory checks
+    # No remote at all (e.g. fresh clone before first fetch) — be safe, run everything
     CLIENT_CHANGED=1
     SERVER_CHANGED=1
     TOOLING_CHANGED=1
@@ -114,7 +127,12 @@ else
 fi
 
 # --- JSON syntax validation ---
-if git rev-parse --verify "$REMOTE_REF" >/dev/null 2>&1; then
+# Use the same REMOTE_REF the directory-change detection above settled on
+# (origin/<branch> preferred, origin/main fallback). Without this, a first
+# push of a new branch falls through to "validate every JSON in the repo,"
+# which on this repo means 2762 Python parses — tens of seconds of churn
+# for a push that might not have touched any JSON at all.
+if [ -n "$REMOTE_REF" ]; then
     JSON_FILES=$(git diff --name-only "$REMOTE_REF"..HEAD -- '*.json' 2>/dev/null || true)
 else
     JSON_FILES=$(git ls-files '*.json')