feat(gitflow): hooks in every repo, no per-project step

Global: `make link` generates githooks/ from lib/gitflow.sh and sets git's
global core.hooksPath to ~/.claude/githooks, so every repo on the machine
runs the pre-commit protection and the post-commit / post-merge push, even
one that never ran gitflow init. A repo's own local core.hooksPath still
wins, so hooks/session-start.sh calls `gitflow reconcile-hooks` once per
session and rewrites a .githooks/ that lags the lib (LRN-114 automated);
the pre-commit exemption now covers .githooks/** next to .claude/**.

Per-repo opt-outs for a foreign clone: `git config gitflow.protect false`
(branch model) and `git config gitflow.autopush false` (push). Both, and
the GIT_CONFIG_GLOBAL= / GIT_CONFIG= env bypass, are static deny rules.

`make test` and the two suites that commit on main export
GIT_CONFIG_GLOBAL=/dev/null so the machine's global hooks never fire in
throwaway repos. doctor gains "Git hooks" (global setting, githooks/ equal
to the emitters) and "Scratchpad" (warn when TMPDIR sits on a tmpfs with
usrquota: systemd caps each user at 80% of it, which killed two shells
today, BLK-021). Tests: T18h, T19d, T20 (reconcile), T21 (whitelist and
protect opt-out); this repo's own stale .githooks/ refreshed.

githooks/post-commit

@@ -0,0 +1,15 @@
+#!/bin/sh
+# gitflow post-commit — generated by gitflow_init. Do not hand-edit.
+# Pushes every commit as it lands (BDR-095): a remote only backs up what it
+# holds. Never fails the commit: no origin / offline / refused → warning only.
+# Opt out for one command with GITFLOW_NO_PUSH=1 (throwaway repos, tests).
+[ "${GITFLOW_NO_PUSH:-0}" = 1 ] && exit 0
+# Per-repo opt-out (no push rights on a foreign clone): git config gitflow.autopush false
+[ "$(git config --bool --default true gitflow.autopush)" = false ] && exit 0
+git remote get-url origin >/dev/null 2>&1 || exit 0
+br=$(git symbolic-ref --short -q HEAD 2>/dev/null) || exit 0   # detached HEAD — nothing to track
+if command -v timeout >/dev/null 2>&1; then t="timeout ${GITFLOW_PUSH_TIMEOUT:-30}"; else t=""; fi
+if $t git push -q -u --follow-tags origin "$br" >/dev/null 2>&1; then exit 0; fi
+echo "gitflow post-commit: push of '$br' FAILED — this commit exists only on this disk." >&2
+echo "  Push by hand: git push -u origin $br   (rejected as non-fast-forward? never force-push; ask first)" >&2
+exit 0

githooks/post-merge

@@ -0,0 +1,15 @@
+#!/bin/sh
+# gitflow post-merge — generated by gitflow_init. Do not hand-edit.
+# Pushes every commit as it lands (BDR-095): a remote only backs up what it
+# holds. Never fails the commit: no origin / offline / refused → warning only.
+# Opt out for one command with GITFLOW_NO_PUSH=1 (throwaway repos, tests).
+[ "${GITFLOW_NO_PUSH:-0}" = 1 ] && exit 0
+# Per-repo opt-out (no push rights on a foreign clone): git config gitflow.autopush false
+[ "$(git config --bool --default true gitflow.autopush)" = false ] && exit 0
+git remote get-url origin >/dev/null 2>&1 || exit 0
+br=$(git symbolic-ref --short -q HEAD 2>/dev/null) || exit 0   # detached HEAD — nothing to track
+if command -v timeout >/dev/null 2>&1; then t="timeout ${GITFLOW_PUSH_TIMEOUT:-30}"; else t=""; fi
+if $t git push -q -u --follow-tags origin "$br" >/dev/null 2>&1; then exit 0; fi
+echo "gitflow post-commit: push of '$br' FAILED — this commit exists only on this disk." >&2
+echo "  Push by hand: git push -u origin $br   (rejected as non-fast-forward? never force-push; ask first)" >&2
+exit 0

githooks/pre-commit

@@ -0,0 +1,41 @@
+#!/bin/sh
+# gitflow pre-commit — generated by gitflow_init. Do not hand-edit.
+# Mirrors gitflow_protected_base (lib/gitflow.sh). Drift caught by T10.
+gd=$(git rev-parse --git-dir)
+br=$(git symbolic-ref --short -q HEAD 2>/dev/null)
+
+git rev-parse --verify -q HEAD >/dev/null 2>&1 || exit 0   # root commit — allow
+[ -f "$gd/MERGE_HEAD" ] && exit 0                          # merge in progress — allow
+
+# Secret backstop (job7) — any branch, not just protected ones. Non-blocking
+# if gitleaks isn't installed; auto-discovers ./.gitleaks.toml (repo root).
+if command -v gitleaks >/dev/null 2>&1; then
+  if ! gitleaks git --staged --no-banner >/dev/null 2>&1; then
+    echo "gitflow pre-commit: BLOCKED — gitleaks found a secret in staged changes." >&2
+    echo "  Details: gitleaks git --staged --no-banner" >&2
+    echo "  Genuine false-positive? add an allowlist rule to .gitleaks.toml — never bypass with --no-verify." >&2
+    exit 1
+  fi
+else
+  echo "gitflow pre-commit: gitleaks not installed — secret scan skipped (https://github.com/gitleaks/gitleaks)." >&2
+fi
+
+# Per-repo opt-out of the branch model (a clone of a foreign project):
+#   git config gitflow.protect false
+[ "$(git config --bool --default true gitflow.protect)" = false ] && exit 0
+
+case "$br" in
+  main|develop) ;;                        # protected — keep checking
+  *) exit 0 ;;                                              # working branch — allow
+esac
+
+# whitelist: all-staged-under-.claude/ (memory/doc/deploy helpers) or
+# .githooks/ (the hooks themselves, refreshed by the lib) — allow
+if [ -z "$(git diff --cached --name-only | grep -vE '^\.(claude|githooks)/' | head -1)" ]; then
+  exit 0
+fi
+
+echo "gitflow pre-commit: BLOCKED — direct commit on '$br'." >&2
+echo "  Branch from the right base (feature/bugfix->develop, hotfix->main), or merge." >&2
+echo "  (.claude/** and .githooks/** commits are exempt; foreign clone? git config gitflow.protect false)" >&2
+exit 1