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>

AGENTS.md

@@ -5,16 +5,19 @@
 
 ## Navigation
 ```text
-src/
-├── main.rs, config.rs, cache.rs, error.rs, curl_impersonate.rs
-├── cli/        clap commands: stocks, ownership, config, cache
-├── api/        providers: msn/ (default), yahoo/ (history/OHLCV)
-├── analysis/   technical, fundamental, signals
-├── ownership/  xlsx + pdf parsers, archive (ZIP/TXT), remote discovery,
-│               snapshot sync, db (SQLite/FTS5), entities, search, graph
-└── output/     table.rs, json.rs
-tests/          cli.rs (behavior), golden.rs + golden/ (output parity), fixtures/
-scripts/        smoke, installer, and ownership snapshot publisher
+crates/idx-core/            library: all data access and analysis
+├── src/api/                providers: msn/ (default), yahoo/ (history/OHLCV)
+├── src/analysis/           technical, fundamental, signals
+├── src/ownership/          xlsx + pdf parsers, archive (ZIP/TXT), remote discovery,
+│                           snapshot sync, db (SQLite/FTS5), entities, search, graph
+├── src/{cache,config,error,curl_impersonate}.rs, lib.rs (runtime)
+└── tests/fixtures/         shared fixtures (also read by the mock provider)
+crates/idx-cli/             binary `idx`
+├── src/cli/                clap commands: stocks, ownership, config, cache
+├── src/config.rs           IdxConfig: output format and color resolution
+├── src/output/             table.rs, json.rs, style.rs
+└── tests/                  cli.rs (behavior), golden.rs + golden/ (output parity)
+scripts/                    smoke, installer, and ownership snapshot publisher
 ```
 
 Docs: