refactor(core): Rename GiError to LoreError and add search infrastructure

Mechanical rename of GiError -> LoreError across the core module to
match the project's rebranding from gitlab-inbox to gitlore/lore.
Updates the error enum name, all From impls, and the Result type alias.

Additionally introduces:

- New error variants for embedding pipeline: OllamaUnavailable,
  OllamaModelNotFound, EmbeddingFailed, EmbeddingsNotBuilt. Each
  includes actionable suggestions (e.g., "ollama serve", "ollama pull
  nomic-embed-text") to guide users through recovery.

- New error codes 14-16 for programmatic handling of Ollama failures.

- Savepoint-based migration execution in db.rs: each migration now
  runs inside a SQLite SAVEPOINT so a failed migration rolls back
  cleanly without corrupting the schema_version tracking. Previously
  a partial migration could leave the database in an inconsistent
  state.

- core::backoff module: exponential backoff with jitter utility for
  retry loops in the embedding pipeline and discussion queues.

- core::project module: helper for resolving project IDs and paths
  from the local database, used by the document regenerator and
  search filters.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/core/project.rs

@@ -0,0 +1,163 @@
+use rusqlite::Connection;
+
+use super::error::{LoreError, Result};
+
+/// Resolve a project string to a project_id using cascading match:
+/// 1. Exact match on path_with_namespace
+/// 2. Case-insensitive exact match
+/// 3. Suffix match (only if unambiguous)
+/// 4. Error with available projects list
+pub fn resolve_project(conn: &Connection, project_str: &str) -> Result<i64> {
+    // Step 1: Exact match
+    let exact = conn.query_row(
+        "SELECT id FROM projects WHERE path_with_namespace = ?1",
+        rusqlite::params![project_str],
+        |row| row.get::<_, i64>(0),
+    );
+    if let Ok(id) = exact {
+        return Ok(id);
+    }
+
+    // Step 2: Case-insensitive exact match
+    let ci = conn.query_row(
+        "SELECT id FROM projects WHERE LOWER(path_with_namespace) = LOWER(?1)",
+        rusqlite::params![project_str],
+        |row| row.get::<_, i64>(0),
+    );
+    if let Ok(id) = ci {
+        return Ok(id);
+    }
+
+    // Step 3: Suffix match (unambiguous)
+    let mut suffix_stmt = conn.prepare(
+        "SELECT id, path_with_namespace FROM projects
+         WHERE path_with_namespace LIKE '%/' || ?1
+            OR path_with_namespace = ?1"
+    )?;
+    let suffix_matches: Vec<(i64, String)> = suffix_stmt
+        .query_map(rusqlite::params![project_str], |row| {
+            Ok((row.get(0)?, row.get(1)?))
+        })?
+        .collect::<std::result::Result<Vec<_>, _>>()?;
+
+    match suffix_matches.len() {
+        1 => return Ok(suffix_matches[0].0),
+        n if n > 1 => {
+            let matching: Vec<String> = suffix_matches.iter().map(|(_, p)| p.clone()).collect();
+            return Err(LoreError::Other(format!(
+                "Project '{}' is ambiguous. Matching projects:\n{}\n\nHint: Use the full path, e.g., --project={}",
+                project_str,
+                matching.iter().map(|p| format!("  {}", p)).collect::<Vec<_>>().join("\n"),
+                matching[0]
+            )));
+        }
+        _ => {}
+    }
+
+    // Step 4: No match — list available projects
+    let mut all_stmt = conn.prepare(
+        "SELECT path_with_namespace FROM projects ORDER BY path_with_namespace"
+    )?;
+    let all_projects: Vec<String> = all_stmt
+        .query_map([], |row| row.get(0))?
+        .collect::<std::result::Result<Vec<_>, _>>()?;
+
+    if all_projects.is_empty() {
+        return Err(LoreError::Other(format!(
+            "Project '{}' not found. No projects have been synced yet.\n\nHint: Run 'lore ingest' first.",
+            project_str
+        )));
+    }
+
+    Err(LoreError::Other(format!(
+        "Project '{}' not found.\n\nAvailable projects:\n{}\n\nHint: Use the full path, e.g., --project={}",
+        project_str,
+        all_projects.iter().map(|p| format!("  {}", p)).collect::<Vec<_>>().join("\n"),
+        all_projects[0]
+    )))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    fn setup_db() -> Connection {
+        let conn = Connection::open_in_memory().unwrap();
+        conn.execute_batch("
+            CREATE TABLE projects (
+                id INTEGER PRIMARY KEY,
+                gitlab_project_id INTEGER UNIQUE NOT NULL,
+                path_with_namespace TEXT NOT NULL,
+                default_branch TEXT,
+                web_url TEXT,
+                created_at INTEGER,
+                updated_at INTEGER,
+                raw_payload_id INTEGER
+            );
+            CREATE INDEX idx_projects_path ON projects(path_with_namespace);
+        ").unwrap();
+        conn
+    }
+
+    fn insert_project(conn: &Connection, id: i64, path: &str) {
+        conn.execute(
+            "INSERT INTO projects (id, gitlab_project_id, path_with_namespace) VALUES (?1, ?2, ?3)",
+            rusqlite::params![id, id * 100, path],
+        ).unwrap();
+    }
+
+    #[test]
+    fn test_exact_match() {
+        let conn = setup_db();
+        insert_project(&conn, 1, "backend/auth-service");
+        let id = resolve_project(&conn, "backend/auth-service").unwrap();
+        assert_eq!(id, 1);
+    }
+
+    #[test]
+    fn test_case_insensitive() {
+        let conn = setup_db();
+        insert_project(&conn, 1, "backend/auth-service");
+        let id = resolve_project(&conn, "Backend/Auth-Service").unwrap();
+        assert_eq!(id, 1);
+    }
+
+    #[test]
+    fn test_suffix_unambiguous() {
+        let conn = setup_db();
+        insert_project(&conn, 1, "backend/auth-service");
+        insert_project(&conn, 2, "frontend/web-ui");
+        let id = resolve_project(&conn, "auth-service").unwrap();
+        assert_eq!(id, 1);
+    }
+
+    #[test]
+    fn test_suffix_ambiguous() {
+        let conn = setup_db();
+        insert_project(&conn, 1, "backend/auth-service");
+        insert_project(&conn, 2, "frontend/auth-service");
+        let err = resolve_project(&conn, "auth-service").unwrap_err();
+        let msg = err.to_string();
+        assert!(msg.contains("ambiguous"), "Expected ambiguous error, got: {}", msg);
+        assert!(msg.contains("backend/auth-service"));
+        assert!(msg.contains("frontend/auth-service"));
+    }
+
+    #[test]
+    fn test_no_match() {
+        let conn = setup_db();
+        insert_project(&conn, 1, "backend/auth-service");
+        let err = resolve_project(&conn, "nonexistent").unwrap_err();
+        let msg = err.to_string();
+        assert!(msg.contains("not found"), "Expected not found error, got: {}", msg);
+        assert!(msg.contains("backend/auth-service"));
+    }
+
+    #[test]
+    fn test_empty_projects() {
+        let conn = setup_db();
+        let err = resolve_project(&conn, "anything").unwrap_err();
+        let msg = err.to_string();
+        assert!(msg.contains("No projects have been synced"));
+    }
+}