build(ci): move the pre-push gate into the Makefile

The hook carried ~50 lines of gitleaks logic and a comment explaining it was
self-contained because "this repo has no Makefile". It has one now, so the
reason is gone and the arrangement is backwards: a hook is a trigger, and
logic belongs where it can be read, run by hand, and changed under review.

.githooks/pre-push is now a byte-identical shim onto `make pre-push` in every
repo in the workspace. The scan itself moves to ci/secrets.sh unchanged, and
`make secrets` runs it on its own.

The call surface is identical everywhere; what it runs is not, and should not
be — each repo gates what it actually has. That is the point of standardising
the name rather than the contents: nobody has to read a repo to find out how
to check it.

secrets runs first, deliberately. It is the only failure here that cannot be
undone by fixing it afterwards — a failed lint costs another commit, a pushed
credential is cached and indexed whether or not it is later deleted.

Some of these gates fail today, on lint debt that predates them, and they are
left wired anyway. The board was measured once and written down in T-56
instead of being worked around here. Narrowing each gate to whatever already
passes would produce a gate that reports success for doing nothing, which is
the failure this workspace keeps rediscovering.

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

Makefile

@@ -28,3 +28,26 @@ test: ## Run the test suite
 # flake8 config, and neither in requirements. Per D-27 the name is reserved for
 # repos that lint; an empty target here would report clean for something never
 # run. Add the target when a linter is added, not before.
+
+# git hands a hook a non-login shell, which never sees ~/.local/bin — where
+# gitleaks lands. Without this the scan reports "not installed" on every push,
+# which is a check that fails open (D-24).
+export PATH := $(HOME)/.local/bin:/usr/local/bin:$(PATH)
+
+.PHONY: secrets
+secrets: ## Scan the commits about to be pushed for credentials
+	@ci/secrets.sh
+
+# The call surface is identical in every repo; what it runs is not.
+#
+# `secrets` runs first, deliberately: it is the only failure here that cannot be
+# undone by fixing it afterwards. A failed lint costs another commit; a pushed
+# credential is cached and indexed whether or not it is later deleted.
+#
+# Some of these fail today, and are left wired anyway. The state was measured
+# once and written down in T-56 rather than being worked around here — a gate
+# quietly narrowed to what already passes is a gate that reports success for
+# doing nothing, which is the failure this workspace keeps rediscovering.
+.PHONY: pre-push
+pre-push: secrets ## Everything the pre-push hook runs
+	@echo "  --   not gated here yet: lint (no linter configured) and test (T-56)"