Rename the program to sww and its deciding daemon to discriminator (closes #218)

The program is now sww, built from cmd/sww, with two modes: sww rproxy and
sww discriminator. servewaf becomes discriminator everywhere it names that
daemon: the package (internal/discriminator), its types, functions, files, the
discriminator_line log field, and its docs and tests.

smallwebwaf is left only where sneak's directive allows it: the documents'
product name, the git.eeqj.de/sneak/smallwebwaf URLs, and the Go module path
sneak.berlin/go/smallwebwaf. Everywhere else a name containing it takes the sww
form: the package (internal/sww), metric names (sww_*), the X-Sww-* headers,
the /_sww/ admin endpoints, the OS user, and the state and rules directories.
The SWWAF_ environment variables take the SWW_ form.

No logic changes. make check passes.

Model: deepseek-v4-pro

Dockerfile

@@ -87,7 +87,7 @@ COPY . .
 # .git present, a version that is still empty, dev or unknown fails the
 # build: git is missing or could not read the checkout. The no_fs_access
 # tag keeps Coraza from writing the files of a multipart body to the
-# system's temporary directory, since smallwebwaf writes only to its state
+# system's temporary directory, since sww writes only to its state
 # directory.
 ARG VERSION
 RUN VERSION="${VERSION:-$(git describe --tags --always)}"; \
@@ -99,7 +99,7 @@ RUN VERSION="${VERSION:-$(git describe --tags --always)}"; \
     fi; \
     CGO_ENABLED=0 go build -tags no_fs_access -trimpath \
         -ldflags="-s -w -X main.Version=${VERSION}" \
-        -o /usr/local/bin/smallwebwaf ./cmd/smallwebwaf
+        -o /usr/local/bin/sww ./cmd/sww
 
 # runsvinit, the image's entrypoint, built at the last commit of its
 # archived repository. It has no go.mod, and `go build` of its directory
@@ -118,7 +118,7 @@ RUN git checkout --quiet --detach b4b2c785308b1ce785b6155c7fe5f16879080193 \
         -o /usr/local/bin/runsvinit .
 
 # The image, described under "Deployment" in SPEC.md. It runs rproxy unless
-# SMALLWEBWAF_COMMAND says servewaf, and an app's Dockerfile can build FROM it.
+# SWW_COMMAND says discriminator, and an app's Dockerfile can build FROM it.
 # It is the last stage, so a plain `docker build .` builds it.
 #
 # ubuntu 26.04, 2026-09-27
@@ -166,27 +166,27 @@ RUN curl -fsSL -o /tmp/nixexprs.tar.xz \
 ENV PATH=${PATH}:/nix/var/nix/profiles/default/bin
 
 COPY --from=runsvinit /usr/local/bin/runsvinit /usr/local/bin/runsvinit
-COPY --from=builder /usr/local/bin/smallwebwaf /usr/local/bin/smallwebwaf
+COPY --from=builder /usr/local/bin/sww /usr/local/bin/sww
 
 # 65532 is above the uids Ubuntu keeps for system users, which end at
 # 999; useradd warns about it unless --key raises that end for this call.
-RUN groupadd --system --gid 65532 smallwebwaf \
+RUN groupadd --system --gid 65532 sww \
     && useradd --system --key SYS_UID_MAX=65532 --uid 65532 \
-        --gid smallwebwaf --no-create-home --shell /usr/sbin/nologin \
-        smallwebwaf
+        --gid sww --no-create-home --shell /usr/sbin/nologin \
+        sww
 
-# The state files' directory, SWWAF_STATE_DIR by default, where a volume
+# The state files' directory, SWW_STATE_DIR by default, where a volume
 # is mounted to keep them across deploys. The run script gives it to the
-# smallwebwaf user at each start of servewaf.
-RUN mkdir /var/lib/smallwebwaf
+# sww user at each start of discriminator.
+RUN mkdir /var/lib/sww
 
-# The default rule file, in SWWAF_RULES_DIR by default, where a Dockerfile
+# The default rule file, in SWW_RULES_DIR by default, where a Dockerfile
 # built FROM this image can copy rule files of its own beside it.
-COPY share/rules.d/00-default.rules /etc/smallwebwaf/rules.d/00-default.rules
+COPY share/rules.d/00-default.rules /etc/sww/rules.d/00-default.rules
 
 # runsvinit starts runit's runsvdir on /etc/service, where Ubuntu's sv
 # looks too.
-COPY --chmod=755 share/smallwebwaf.run /etc/service/smallwebwaf/run
+COPY --chmod=755 share/sww.run /etc/service/sww/run
 
 EXPOSE 8080
 
@@ -194,6 +194,6 @@ EXPOSE 8080
 # check runs every second from the start until it first passes, for up
 # to a minute, and every 30 seconds after that.
 HEALTHCHECK --start-period=1m --start-interval=1s \
-    CMD ["/usr/local/bin/smallwebwaf", "healthcheck"]
+    CMD ["/usr/local/bin/sww", "healthcheck"]
 
 ENTRYPOINT ["/usr/local/bin/runsvinit"]