feat(graphify): threshold signal from 200 tracked code files, the banner informs and the user decides

lib/graphify-gate.sh counts tracked code files (graphify's AST extension set, vendored trees excluded) and, from 200 with no graphify-out/graph.json, prints one banner-sized line; session-start shows it with the /graphify hint. Nothing is built, installed or updated: the rule is the user's (BDR-097), grounded in the LRN-162 measurements (AST build 2.3 s, 0 tokens, a query 2 to 3k tokens). Doctrine section and plugin-advisor thresholds follow the same rule; graphify claude install stays rejected. Test: 11 checks. GRAPHIFY_MIN_CODE_FILES overrides the threshold.

lib/graphify-gate.sh

@@ -0,0 +1,41 @@
+#!/usr/bin/env bash
+# graphify-gate.sh — deterministic "propose graphify" signal (BDR-097).
+#
+# Rule (user, 2026-09-24): graphify only from 200 tracked code files. Below,
+# grep + read is cheaper than a graph. The signal INFORMS, the user DECIDES:
+# nothing here builds, installs or updates a graph.
+#
+# Sourced (functions) or executed: `graphify-gate.sh [dir]` prints one short
+# line (banner-sized) and exits 0 when <dir>'s repo passes the threshold and has
+# no graphify-out/graph.json; silent, rc 1 otherwise. GRAPHIFY_MIN_CODE_FILES
+# overrides the threshold (tests).
+
+GRAPHIFY_MIN_CODE_FILES="${GRAPHIFY_MIN_CODE_FILES:-200}"
+# Extensions graphify extracts by AST (tree-sitter): the proxy for "code file".
+GRAPHIFY_CODE_EXT='py|js|mjs|cjs|ts|tsx|jsx|vue|svelte|astro|php|go|rs|java|kt|c|h|cpp|hpp|cc|cs|rb|swift|scala|sh|bash|lua|sql'
+# Vendored trees sometimes committed; never the project's own code.
+GRAPHIFY_VENDOR_DIRS='vendor|node_modules|third_party|dist|build'
+
+# graphify_code_file_count [dir] → tracked code files, vendored trees excluded.
+# Tracked only (git ls-files): gitignored deps and build output never count.
+graphify_code_file_count() {
+  git -C "${1:-.}" ls-files 2>/dev/null \
+    | grep -v -E "(^|/)($GRAPHIFY_VENDOR_DIRS)/" \
+    | grep -E -c "\.($GRAPHIFY_CODE_EXT)$"
+}
+
+# graphify_gate [dir] → "graphify? N code files ≥ T, no graph" + rc 0 when the
+# repo passes the threshold without a graph; silent rc 1 otherwise.
+graphify_gate() {
+  local root n
+  root=$(git -C "${1:-.}" rev-parse --show-toplevel 2>/dev/null) || return 1
+  [ -f "$root/graphify-out/graph.json" ] && return 1     # graph exists — nothing to propose
+  n=$(graphify_code_file_count "$root")
+  [ "$n" -ge "$GRAPHIFY_MIN_CODE_FILES" ] || return 1
+  printf 'graphify? %s code files ≥ %s, no graph\n' "$n" "$GRAPHIFY_MIN_CODE_FILES"
+}
+
+if [ "${BASH_SOURCE[0]}" = "${0}" ]; then
+  set -uo pipefail
+  graphify_gate "${1:-.}"
+fi