Add secret.Warn() calls for all silent anomalous conditions

Audit of the codebase found 9 locations where errors or anomalous
conditions were silently swallowed or only logged via Debug(). Users
should be informed when something unexpected happens, even if the
program can continue.

Changes:
- DetermineStateDir: warn on config dir fallback to ~/.config
- info_helper: warn when vault/secret stats cannot be read
- unlockers list: warn on metadata read/parse failures (fixes FIXMEs)
- unlockers list: warn on fallback ID generation
- checkUnlockerExists: warn on errors during duplicate checking
- completions: warn on unlocker metadata read/parse failures
- version list: upgrade metadata load failure from Debug to Warn
- secrets: upgrade file close failure from Debug to Warn
- version naming: warn on malformed version directory names

Closes #19

internal/cli/completions.go

@@ -71,6 +71,8 @@ func getUnlockerIDsCompletionFunc(fs afero.Fs, stateDir string) func(
 			unlockersDir := filepath.Join(vaultDir, "unlockers.d")
 			files, err := afero.ReadDir(fs, unlockersDir)
 			if err != nil {
+				secret.Warn("Could not read unlockers directory during completion", "error", err)
+
 				continue
 			}
 
@@ -85,11 +87,15 @@ func getUnlockerIDsCompletionFunc(fs afero.Fs, stateDir string) func(
 				// Check if this is the right unlocker by comparing metadata
 				metadataBytes, err := afero.ReadFile(fs, metadataPath)
 				if err != nil {
+					secret.Warn("Could not read unlocker metadata during completion", "path", metadataPath, "error", err)
+
 					continue
 				}
 
 				var diskMetadata secret.UnlockerMetadata
 				if err := json.Unmarshal(metadataBytes, &diskMetadata); err != nil {
+					secret.Warn("Could not parse unlocker metadata during completion", "path", metadataPath, "error", err)
+
 					continue
 				}