feat(guardrails): push every commit, static deny for destructive tools, brief carries no user authority

Layer C of the plan written after the 2026-09-21 wipe (BDR-095): a reviewer
sub-agent traced `lftp mirror --delete` against a local file:// tree, the
prose tiers named neither lftp nor a local trace, the brief had authorized
it, and four days of commits had never left the machine.

- gitflow: `start` pushes the branch with its upstream, merge targets are
  pushed after each merge, and `init`/`install-hook` write post-commit and
  post-merge hooks that push every commit as it lands (warn, never block;
  GITFLOW_NO_PUSH=1 for throwaway repos). T18 + T19 (installed == emitted).
- hooks/unpushed-guard.sh on SessionStart and Stop: branch ahead of its
  upstream, no upstream, or no origin. Non-blocking systemMessage.
- settings.json: static deny for transfer and mirror tools, rsync --delete,
  xargs rm, pipe-to-shell, chmod/chown -R, sudo/doas/pkexec, disk tools,
  chattr, docker volume drops/prune/--privileged/socket/-v /:, git history
  destruction, --no-verify and core.hooksPath; new hard_deny "destructive
  tool against a local path, brief carries no user authority"; soft_deny
  reworded + discarding uncommitted work; environment records the incident.
- CLAUDE.global.md "Destructive tools & data loss"; the four report-only
  agents trace by reading, never by running, whatever the brief says.
- lib/tests/guard-bash.test.sh: executable spec of the PreToolUse guard
  (214 cases). The hook itself is not shipped (BLK-022); the spec skips.

.githooks/post-commit

@@ -0,0 +1,13 @@
+#!/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).
+[ "${GITFLOW_NO_PUSH:-0}" = 1 ] && exit 0
+git remote get-url origin >/dev/null 2>&1 || exit 0
+br=$(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 +1,13 @@
+#!/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).
+[ "${GITFLOW_NO_PUSH:-0}" = 1 ] && exit 0
+git remote get-url origin >/dev/null 2>&1 || exit 0
+br=$(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