fix(error): replace misleading Database error suggestions

The Database(rusqlite::Error) catch-all variant was suggesting
'lore reset --yes' for ALL database errors, including transient
SQLITE_BUSY lock contention. This was wrong on two counts:
1. `lore reset` is not implemented (prints "not yet implemented")
2. Nuking the database is not the fix for a transient lock

Changes:
- Detect SQLITE_BUSY specifically via sqlite_error_code() and provide
  targeted advice: "Another process has the database locked" with
  common causes (cron sync, concurrent lore command)
- Map SQLITE_BUSY to ErrorCode::DatabaseLocked (exit code 9) instead
  of DatabaseError (exit code 10) — semantically correct
- Set BUSY actions to ["lore cron status"] (diagnostic) instead of
  the useless "lore sync --force" (--force overrides the app-level
  lock table, but SQLITE_BUSY fires before that table is even reached)
- Fix MigrationFailed suggestion: also referenced non-existent
  'lore reset', now says "try again" with lore migrate / lore doctor
- Non-BUSY database errors get a simpler suggestion pointing to
  lore doctor (no more phantom reset command)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/core/error.rs

@@ -180,7 +180,13 @@ impl LoreError {
             Self::DatabaseLocked { .. } => ErrorCode::DatabaseLocked,
             Self::MigrationFailed { .. } => ErrorCode::MigrationFailed,
             Self::TokenNotSet { .. } => ErrorCode::TokenNotSet,
-            Self::Database(_) => ErrorCode::DatabaseError,
+            Self::Database(e) => {
+                if e.sqlite_error_code() == Some(rusqlite::ErrorCode::DatabaseBusy) {
+                    ErrorCode::DatabaseLocked
+                } else {
+                    ErrorCode::DatabaseError
+                }
+            }
             Self::Http(_) => ErrorCode::GitLabNetworkError,
             Self::Json(_) => ErrorCode::InternalError,
             Self::Io(_) => ErrorCode::IoError,
@@ -218,14 +224,20 @@ impl LoreError {
                 "Wait for other sync to complete or use --force.\n\n  Example:\n    lore ingest --force\n    lore ingest issues --force",
             ),
             Self::MigrationFailed { .. } => Some(
-                "Check database file permissions or reset with 'lore reset'.\n\n  Example:\n    lore migrate\n    lore reset --yes",
+                "Check database file permissions and try again.\n\n  Example:\n    lore migrate\n    lore doctor",
             ),
             Self::TokenNotSet { .. } => Some(
                 "Set your token:\n\n  lore token set\n\n  Or export to your shell:\n\n  export GITLAB_TOKEN=glpat-xxxxxxxxxxxx\n\n  Your token needs the read_api scope.",
             ),
-            Self::Database(_) => Some(
-                "Check database file permissions or reset with 'lore reset'.\n\n  Example:\n    lore doctor\n    lore reset --yes",
-            ),
+            Self::Database(e) => {
+                if e.sqlite_error_code() == Some(rusqlite::ErrorCode::DatabaseBusy) {
+                    Some(
+                        "Another process has the database locked. Wait a moment and retry.\n\n  Common causes:\n    - A cron sync is running (lore cron status)\n    - Another lore command is active",
+                    )
+                } else {
+                    Some("Check database file permissions.\n\n  Example:\n    lore doctor")
+                }
+            }
             Self::Http(_) => Some("Check network connection"),
             Self::NotFound(_) => {
                 Some("Verify the entity exists.\n\n  Example:\n    lore issues\n    lore mrs")
@@ -267,6 +279,11 @@ impl LoreError {
             Self::OllamaUnavailable { .. } => vec!["ollama serve"],
             Self::OllamaModelNotFound { .. } => vec!["ollama pull nomic-embed-text"],
             Self::DatabaseLocked { .. } => vec!["lore ingest --force"],
+            Self::Database(e)
+                if e.sqlite_error_code() == Some(rusqlite::ErrorCode::DatabaseBusy) =>
+            {
+                vec!["lore cron status"]
+            }
             Self::EmbeddingsNotBuilt => vec!["lore embed"],
             Self::EmbeddingFailed { .. } => vec!["lore embed --retry-failed"],
             Self::MigrationFailed { .. } => vec!["lore migrate"],