docs: tighten receipt-store comments

Cut WHAT-narration, #3237 issue refs, version-compat justifications, and
contract repetition. The ReceiptStoreConfig type godoc owns the
KeepRecent-is-a-no-op explanation; the archive override site, legacy
struct, and tests no longer repeat it. Reference upstream symbols by
name (flagRSMisnamedBackend) instead of paraphrasing.

Net -15 hand-written comment lines, no behavior change.

Author: bdchatham

config.go

@@ -341,11 +341,9 @@ type StateStoreConfig struct {
 	EVMDBDirectory       string    `toml:"evm_db_directory"`
 }
 
-// ReceiptStoreConfig mirrors sei-chain's ReceiptStoreConfig.
-// On post-#3237 sei-chain, KeepRecent is tagged `mapstructure:"-"` upstream
-// and is stamped from base-app min-retain-blocks at startup; the TOML key
-// is silently ignored. We still emit it so the config self-documents the
-// retention intent and remains compatible with pre-#3237 binaries.
+// ReceiptStoreConfig — KeepRecent is silently ignored at runtime;
+// sei-chain tags it `mapstructure:"-"` and stamps the value from base-app
+// min-retain-blocks. Emitted anyway so the TOML documents retention intent.
 type ReceiptStoreConfig struct {
 	Backend              string `toml:"backend"`
 	DBDirectory          string `toml:"db_directory"`

config_test.go

@@ -77,9 +77,6 @@ func TestDefaultForMode_ArchiveKeepsAll(t *testing.T) {
 	if cfg.EVM.MaxTraceLookbackBlocks != -1 {
 		t.Errorf("archive max_trace_lookback_blocks: got %d, want -1", cfg.EVM.MaxTraceLookbackBlocks)
 	}
-	// All three knobs that govern receipt-store retention must evaluate to
-	// "no pruning" — min-retain-blocks=0 (drives ReceiptStore.KeepRecent at
-	// the app layer), pruning="nothing", and prune-interval-seconds=0.
 	if got := cfg.Storage.ReceiptStore.KeepRecent; got != 0 {
 		t.Errorf("archive receipt_store.keep_recent: got %d, want 0", got)
 	}
@@ -89,11 +86,8 @@ func TestDefaultForMode_ArchiveKeepsAll(t *testing.T) {
 }
 
 func TestWriteArchive_ReceiptStoreTOMLKeys(t *testing.T) {
-	// Pin the literal app.toml keys in the [receipt-store] section. A symmetric
-	// tag typo across toLegacyApp / fromLegacy round-trips cleanly but produces
-	// an app.toml seid won't accept (e.g., flagRSMisnamedBackend rejects
-	// "backend" without the rs- prefix at startup). Tag-renaming refactors
-	// must update this list.
+	// Symmetric tag typos round-trip cleanly but produce a TOML seid rejects;
+	// pin the literal upstream key tokens.
 	dir := t.TempDir()
 	if err := WriteConfigToDir(DefaultForMode(ModeArchive), dir); err != nil {
 		t.Fatalf("WriteConfigToDir: %v", err)
@@ -120,15 +114,13 @@ func TestWriteArchive_ReceiptStoreTOMLKeys(t *testing.T) {
 			t.Errorf("app.toml missing receipt-store key %q", k)
 		}
 	}
-	// Reject the misnamed-backend variant — sei-chain hard-errors on it.
+	// flagRSMisnamedBackend hard-errors on the unprefixed key at startup.
 	if strings.Contains(out, "\nbackend = ") {
 		t.Errorf("app.toml emits unprefixed `backend = ` which sei-chain rejects")
 	}
 }
 
 func TestDefaultForMode_ReceiptStoreDefaults(t *testing.T) {
-	// Non-archive modes match sei-chain's documented defaults so the emitted
-	// TOML matches operator expectations on both pre- and post-#3237 binaries.
 	rs := DefaultForMode(ModeFull).Storage.ReceiptStore
 
 	if rs.Backend != BackendPebbleDB {

defaults.go

@@ -308,12 +308,8 @@ func applyArchiveOverrides(cfg *SeiConfig) {
 
 	cfg.Storage.PruningStrategy = PruningNothing
 	cfg.Storage.StateStore.KeepRecent = 0
-	// All three knobs that govern receipt retention are pinned to "no
-	// pruning" intent. On post-#3237 sei-chain only MinRetainBlocks=0 is
-	// load-bearing (KeepRecent is mapstructure:"-" and PruneIntervalSeconds=0
-	// is silently floored on the pebbledb backend); on pre-#3237 binaries
-	// the receipt-store keys are what take effect. Setting all three keeps
-	// the emitted TOML self-documenting and version-agnostic.
+	// Only MinRetainBlocks disables receipt pruning at runtime; the next two
+	// are emitted to document intent (see ReceiptStoreConfig).
 	cfg.Chain.MinRetainBlocks = 0
 	cfg.Storage.ReceiptStore.KeepRecent = 0
 	cfg.Storage.ReceiptStore.PruneIntervalSeconds = 0

legacy.go

@@ -282,9 +282,8 @@ type legacyStateStore struct {
 	EVMDBDirectory       string `toml:"ss-evm-db-directory"`
 }
 
-// legacyReceiptStore mirrors the keys sei-chain reads from app.toml.
-// Note: rs-backend is asymmetric — only Backend carries the rs- prefix
-// upstream. The other keys do not.
+// rs-backend is asymmetric upstream — only Backend carries the rs- prefix.
+// flagRSMisnamedBackend rejects the unprefixed `backend` key at startup.
 type legacyReceiptStore struct {
 	Backend              string `toml:"rs-backend"`
 	DBDirectory          string `toml:"db-directory"`