SPEC, README and docs rewritten from scratch (closes #154, closes #155, closes #156)

SPEC.md is the only place that says how smallwebwaf behaves and why; docs/ holds lists linking to it; the README is short and links to both. Passed independent review in round 8.

Model: fable-5-1 (writing); opus-5-5 (review, merge)

internal/anomaly/anomaly.go

@@ -1,8 +1,8 @@
 // Package anomaly counts requests and bytes over a minute and an hour, per
 // client, per surrounding netblock, per AS number, for the whole service
 // and per named netblock, and raises an anomaly alert for a count over its
-// threshold, as "Anomaly thresholds" under "Configuration surface" in
-// SPEC.md describes. It refuses and bans nothing. At most 20,000 counters
+// threshold, as "Anomaly thresholds" under "Settings" in SPEC.md
+// describes. It refuses and bans nothing. At most 20,000 counters
 // are kept, in memory, and written to alerts.json and read from it by the
 // state package.
 package anomaly