store, web: cite the source of what they rely on (assumptions part D)

Comments only, no behaviour changed. modernc.org/sqlite v1.60.1 (the
_pragma list on every connection, busy_timeout first; extended result
codes; a deferred BEGIN; multi-statement Exec) and SQLite 3.53.4's
documentation (transactions, WAL, foreign keys, NOCASE, upsert, julianday,
partial indexes); htmx 2.0.4 src/htmx.js; the Fetch and HTML standards for
Sec-Fetch-Site, Origin, SameSite, __Host-, CSP and defer order; Go's
html/template. Comments the source contradicts are corrected - the driver
does not serialise writes (SetMaxOpenConns(1) does), htmx:load fires per
swapped element, no-store does not keep a page out of history.

Left for their own commits: D-S3 a migration two processes can both run,
D-S20 recipient case, D-B3 Origin: null under Referrer-Policy: no-referrer,
D-H5/H6/H7/H9 (audit M11, stage 4).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/web/view/static.go

@@ -16,7 +16,10 @@ import (
 // a response carries no validator at all and the browser is free to guess how
 // long to keep it — which is how a replaced favicon keeps showing the old mark
 // long after a deploy. Hashing the content gives every asset a validator that
-// changes exactly when the asset does.
+// changes exactly when the asset does. RFC 9111 § 4.2.2: without explicit
+// freshness a cache may assign a heuristic lifetime; Go 1.26, net/http fs.go
+// ServeContent(): no Last-Modified for a zero modtime, and an ETag the caller
+// set answers If-None-Match.
 var staticETags = buildStaticETags()
 
 func buildStaticETags() map[string]string {
@@ -50,6 +53,8 @@ func buildStaticETags() map[string]string {
 // handful of small files on a single-operator panel that trade is the right way
 // round — correctness after a deploy matters more than saving the round trip.
 // http.ServeContent answers the conditional request from the ETag we set here.
+// RFC 9111 § 5.2.2.4: no-cache lets a cache store the response but not reuse
+// it without validating it first.
 func StaticHandler() http.Handler {
 	files := http.FileServer(http.FS(assetsFS))
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {