refactor: split into idx-core library and idx-cli binary workspace

Phase 2 of docs/DESIGN.md, no behavior change:

- crates/idx-core (library): api, analysis, cache, config file handling
  and provider selection, curl_impersonate, error, ownership, runtime,
  plus the shared test fixtures. clap derives are behind an optional
  `clap` feature so the library does not require clap.
- crates/idx-cli (binary `idx`): cli/, output/, and IdxConfig (output
  format and color resolution). Package and binary names are unchanged.
- config.rs is split: file read/write and validation move to core; a
  CLI test keeps core's OUTPUT_VALUES in sync with OutputSetting.
- ownership::db::open_db/db_path drop their unused IdxConfig argument.
- One workspace version; shared dependency versions; no third-party
  version changes in Cargo.lock. LICENSE is symlinked into each crate.
- flake: workspace version, new source paths, and a per-crate package
  check (idx-cli is built from its tarball against packaged idx-core,
  since idx-core is not on crates.io yet). CI cache key, release path
  filter, and the golden whitespace-hook exclusion follow the new layout.

Parity: all 143 golden outputs match byte for byte without
regeneration; 157 core + 17 CLI unit tests (173 before plus the new
OUTPUT_VALUES sync test), 62 CLI tests pass. Live A/B against main:
16/16 stocks cases identical; ownership discover got IDX 403 on both
(exit 4 vs 1 is the phase 1 exit-code change).

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

tests/golden/ownership-cross-holders.json.golden

@@ -1,4 +0,0 @@
-exit: 0
---- stdout
-[{"entity":{"id":11,"canonical_name":"ASTRA INTERNATIONAL","entity_type":null,"country":null},"ticker_count":1,"total_bps":7968},{"entity":{"id":14,"canonical_name":"DWIMURIA INVESTAMA ANDALAN","entity_type":null,"country":null},"ticker_count":1,"total_bps":5494},{"entity":{"id":4,"canonical_name":"ADARO STRATEGIC INVESTMENTS","entity_type":null,"country":null},"ticker_count":1,"total_bps":4110},{"entity":{"id":5,"canonical_name":"ALAMTRI RESOURCES INDONESIA TBK PT","entity_type":null,"country":null},"ticker_count":1,"total_bps":1537},{"entity":{"id":7,"canonical_name":"GARIBALDI THOHIR","entity_type":null,"country":null},"ticker_count":1,"total_bps":583},{"entity":{"id":2,"canonical_name":"SARATOGA INVESTAMA SEDAYA","entity_type":null,"country":null},"ticker_count":1,"total_bps":438},{"entity":{"id":9,"canonical_name":"EDWIN SOERYADJAYA","entity_type":null,"country":null},"ticker_count":1,"total_bps":352},{"entity":{"id":8,"canonical_name":"IR. T. PERMADI RACHMAT","entity_type":null,"country":null},"ticker_count":1,"total_bps":348},{"entity":{"id":13,"canonical_name":"YAYASAN ABDI BANGSA","entity_type":null,"country":null},"ticker_count":1,"total_bps":283},{"entity":{"id":10,"canonical_name":"SANDIAGA SALAHUDDIN UNO","entity_type":null,"country":null},"ticker_count":1,"total_bps":204},{"entity":{"id":1,"canonical_name":"PERSADA CAPITAL INVESTAMA","entity_type":null,"country":null},"ticker_count":1,"total_bps":154},{"entity":{"id":12,"canonical_name":"YAYASAN BINA SEJAHTERA WARGA BULOG","entity_type":null,"country":null},"ticker_count":1,"total_bps":135},{"entity":{"id":6,"canonical_name":"FTAG INVESTMENT BANK","entity_type":null,"country":null},"ticker_count":1,"total_bps":129},{"entity":{"id":17,"canonical_name":"ANTHONI SALIM","entity_type":null,"country":null},"ticker_count":1,"total_bps":115},{"entity":{"id":3,"canonical_name":"TRINUGRAHA THOHIR","entity_type":null,"country":null},"ticker_count":1,"total_bps":115},{"entity":{"id":16,"canonical_name":"TRICIPTA MANDHALA GUMILANG","entity_type":null,"country":null},"ticker_count":1,"total_bps":107},{"entity":{"id":15,"canonical_name":"CATURGUWIRATNA SUMAPALA","entity_type":null,"country":null},"ticker_count":1,"total_bps":102}]
---- stderr