autoresearch iter 22: delete lint suppressions that suppress nothing

24 of the 96 nolint directives were dead: they covered findings that no
longer exist. A stale suppression is not inert — it silently claims any
future finding for that linter in that scope, so a real problem raised
there would vanish without anyone noticing. Explanatory prose was kept as
ordinary comments.

Two directives proved load-bearing under the project gate even though
nolintlint reported them unused, and removing them exposed verified
contextcheck false positives: App.Run does forward a sigCtx derived from
the caller's context to Start, and the migration lock renewal must keep
its own deadline because the task context may already be canceled. Both
were restored, narrowed to the live linter, and given the reason the
originals lacked.

backend/plugins/domain/cap/pow/prng.go

@@ -10,7 +10,7 @@ import (
 
 // fnv1a returns the 32-bit FNV-1a hash of a string
 //
-//nolint:mnd // FNV-1a 算法位移常量
+// FNV-1a 算法位移常量
 func fnv1a(str string) uint32 {
 	var hash uint32 = 2166136261
 	for i := 0; i < len(str); i++ {
@@ -22,7 +22,7 @@ func fnv1a(str string) uint32 {
 
 // fnv1aResume resumes FNV-1a hashing from a given state
 //
-//nolint:mnd // FNV-1a 算法位移常量
+// FNV-1a 算法位移常量
 func fnv1aResume(state uint32, str string) uint32 {
 	h := state
 	for i := 0; i < len(str); i++ {
@@ -33,15 +33,13 @@ func fnv1aResume(state uint32, str string) uint32 {
 }
 
 // hashShift computes FNV-1a mix additions
-//
-//nolint:mnd
 func hashShift(h uint32) uint32 {
 	return (h << 1) + (h << 4) + (h << 7) + (h << 8) + (h << 24)
 }
 
 // prngFromHash generates a hex string of specified length using an initial hash state
 //
-//nolint:mnd // xorshift 算法位移常量
+// xorshift 算法位移常量
 func prngFromHash(initialHash uint32, length int) string {
 	state := initialHash
 	var result strings.Builder