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

docs/state-files.md

@@ -1,13 +1,13 @@
 # State files
 
-The five JSON files in `SWWAF_STATE_DIR`, and what each holds. "Persistent
-state" in [`SPEC.md`](../SPEC.md) says how they are written, read and edited.
-Each has a top-level `version` of 1.
+The five JSON files in `SWW_STATE_DIR`, and what each holds. "Persistent state"
+in [`SPEC.md`](../SPEC.md) says how they are written, read and edited. Each has
+a top-level `version` of 1.
 
 ## `bans.json`
 
-Active and past bans: every ban an admin made, and up to `SWWAF_MAX_BANS` of
-those `servewaf` made. Per entry:
+Active and past bans: every ban an admin made, and up to `SWW_MAX_BANS` of those
+`discriminator` made. Per entry:
 
 - `netblock`, `start` and `expires` (`null` for a permanent ban);
 - `cause`: `attack`, `limit`, `admin` or `crowdsec`;
@@ -93,10 +93,10 @@ GeoJS answers, one per line:
 ## Sizes
 
 - `clients.json`: about 1 KiB per client, about 20 MiB at the default
-  `SWWAF_MAX_TRACKED_CLIENTS`. Written every 15 minutes, that is under 2 GiB of
+  `SWW_MAX_TRACKED_CLIENTS`. Written every 15 minutes, that is under 2 GiB of
   disk writes a day.
 - `bans.json`: about 1.2 KiB per ban, at most about 2.5 KiB, so about 6 MiB at
-  the default `SWWAF_MAX_BANS`. Written every 15 minutes, a full file comes to
+  the default `SWW_MAX_BANS`. Written every 15 minutes, a full file comes to
   about 600 MiB of writes a day, and a hundred new bans a day add about 600 MiB
   more.
 - `lookups.json`: about 150 bytes per answer, under 1.5 GiB of writes a day when