refactor(core): move ownership queries, import, and sync into idx-core

Phase 3c of docs/DESIGN.md. `ownership` handlers are now argument
parsing, one idx-core call, and rendering.

- investor.rs: Investor (also Idx::investor()) with releases, ticker,
  entity, search, cross_holders, concentration, flow, changes, graph,
  unresolved, map_alias, merge_entities, discover, sync, and import.
  Import orchestration (input resolution, download, SHA-256 dedup,
  PDF/XLSX/archive parsing, entity resolution, release write) moves
  from the CLI unchanged.
- Typed inputs: ImportSource, HolderSource, ConcentrationRank, and
  parse_report_family, with the same error messages.
- CoreConfig gains an ownership_db override; db::open_db_at opens an
  explicit path. idx-cli no longer depends on rusqlite, sha2, or ureq
  at runtime.
- Behavior note: an invalid `ticker --source` or `concentration --by`
  is now rejected before the database file is opened (and created);
  the error and exit code are unchanged.
- Fix: building idx-cli without the ownership feature no longer warns
  about the ownership-only `blue` style.

All 143 goldens unchanged; 170 core + 7 CLI unit tests and 62 CLI tests
pass; clippy clean for default, release, testing, and no-default
feature sets. Live A/B against main: 16/16 stocks identical; ownership
discover got IDX 403 on both (exit 4 vs 1 is the phase 1 change).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/idx-core/src/config.rs

@@ -85,6 +85,9 @@ pub struct CoreConfig {
     pub fundamental_ttl: u64,
     /// Cache root; `None` resolves `$XDG_CACHE_HOME/idx` or the platform default.
     pub cache_dir: Option<PathBuf>,
+    /// Ownership database; `None` uses `ownership.db_path` from `config.toml`,
+    /// else `$XDG_DATA_HOME/idx/ownership.db`.
+    pub ownership_db: Option<PathBuf>,
     /// Provider diagnostics on stderr.
     pub verbose: bool,
 }
@@ -98,6 +101,7 @@ impl Default for CoreConfig {
             quote_ttl: 300,
             fundamental_ttl: 3600,
             cache_dir: None,
+            ownership_db: None,
             verbose: false,
         }
     }