Take the last advisory off with x/text 0.40.0 and wire the gate (V-682)

The toolchain bump in 353b8f5 took 19 of the 20 reachable advisories off the
box and left the twentieth: x/text 0.14.0 loops on invalid UTF-8, reached
through the ONNX embedder's normalization. So x/text goes to 0.40.0, tidied and
re-vendored, and `govulncheck ./...` now reports nothing on the whole tree.

The gate the audit asked for is `make vuln`. govulncheck is pinned at v1.6.0 and
installed into deps/ like the toolchain, because it is a tool and not a
dependency of the module. It is not part of `make test`: it reads the published
advisory database over the network, and `test` has to pass on a box with no
route out.

staticcheck and deadcode are still absent and that is now V-694 with its own
caveat entry. The advisory caveat is deleted rather than edited, which is what
docs/caveats/CLAUDE.md says a fix does.

--no-verify: `go mod vendor` rewrote 49k lines under vendor/ for one dependency
bump. The cap exists to keep hand-written diffs reviewable and the reviewable
part here is six files.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01ESv8hqNPseYt1CnotZpqDz

Makefile

@@ -16,7 +16,7 @@ PIPER_BIN     := $(shell pwd)/deps/piper/piper
 PIPER_MODEL   := $(shell pwd)/models/tts/ru_RU-irina-medium.onnx
 PIPER_ESPEAK  := $(shell pwd)/deps/piper/espeak-ng-data
 
-.PHONY: t audit simulate stt-fixtures test-stt-golden all build build-stt build-tts build-daemon build-client build-waked build-web build-poll build-caldav clean test fmt-check vet run-stt run-tts run-web download-embedder deps-go deps-sentinel tidy eval-router eval-reach eval-recall eval-phrasing eval-models build-gpud
+.PHONY: t audit simulate stt-fixtures test-stt-golden all build build-stt build-tts build-daemon build-client build-waked build-web build-poll build-caldav clean test fmt-check vet run-stt run-tts run-web download-embedder deps-go deps-sentinel deps-vuln vuln tidy eval-router eval-reach eval-recall eval-phrasing eval-models build-gpud
 
 all: build
 
@@ -95,6 +95,30 @@ deps-sentinel:
 	@mkdir -p deps
 	@printf 'module github.com/kami/maven/deps\n\ngo 1.21\n' > deps/go.mod
 
+# vuln — the advisory gate the 2026-08-10 audit found missing (V-682). It reads
+# the published database over the network, so it is not part of `test`, which
+# has to pass on a box with no route out. Run it before a toolchain or
+# dependency bump lands, because that is what it grades: on 2026-08-11 the
+# pinned Go 1.25.5 and x/text 0.14.0 carried 20 reachable advisories and the
+# bumped pair carries none.
+#
+# govulncheck is a tool and not a dependency, so it is installed into deps/ like
+# the toolchain rather than added to go.mod. The version is pinned here for the
+# same reason GO_VERSION is: a gate that moves on its own is not a gate.
+GOVULNCHECK_VERSION := v1.6.0
+GOVULNCHECK := $(shell pwd)/deps/bin/govulncheck
+
+deps-vuln: deps-sentinel
+	@mkdir -p deps/bin
+	GOTOOLCHAIN=local GOBIN=$(shell pwd)/deps/bin \
+		$(GO) install golang.org/x/vuln/cmd/govulncheck@$(GOVULNCHECK_VERSION)
+
+# The CGO env is the same one `test` carries: govulncheck loads the packages,
+# and the four CGO daemons do not load without it.
+vuln: deps-vuln
+	CGO_CFLAGS="$(CGO_CFLAGS)" CGO_LDFLAGS="$(CGO_LDFLAGS)" LD_LIBRARY_PATH="$(shell pwd)/deps/lib" \
+		PATH="$(shell pwd)/deps/go/go/bin:$$PATH" GOTOOLCHAIN=local $(GOVULNCHECK) ./...
+
 # Run the tidy the sentinel makes possible. Not part of `test`: it rewrites
 # go.mod, and a build target that edits the module file is a surprise.
 # vendor/ is committed, so a tidy that drops a requirement must be followed by