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>

crates/idx-core/tests/fixtures/quotesummary_bbca.json

@@ -0,0 +1,82 @@
+{
+  "quoteSummary": {
+    "result": [
+      {
+        "defaultKeyStatistics": {
+          "forwardPE": {
+            "raw": 23.1,
+            "fmt": "23.10"
+          },
+          "priceToBook": {
+            "raw": 4.6,
+            "fmt": "4.60"
+          },
+          "enterpriseValue": {
+            "raw": 1245000000000000,
+            "fmt": "1.25T"
+          },
+          "trailingEps": {
+            "raw": 384.25,
+            "fmt": "384.25"
+          },
+          "forwardEps": {
+            "raw": 410.18,
+            "fmt": "410.18"
+          }
+        },
+        "financialData": {
+          "trailingPE": {
+            "raw": 25.4,
+            "fmt": "25.40"
+          },
+          "marketCap": {
+            "raw": 1215200000000000,
+            "fmt": "1.22T"
+          },
+          "currentPrice": {
+            "raw": 9875,
+            "fmt": "9,875.00"
+          },
+          "returnOnEquity": {
+            "raw": 0.202,
+            "fmt": "20.20%"
+          },
+          "returnOnAssets": {
+            "raw": 0.038,
+            "fmt": "3.80%"
+          },
+          "profitMargins": {
+            "raw": 0.385,
+            "fmt": "38.50%"
+          },
+          "revenueGrowth": {
+            "raw": 0.118,
+            "fmt": "11.80%"
+          },
+          "earningsGrowth": {
+            "raw": 0.121,
+            "fmt": "12.10%"
+          },
+          "debtToEquity": {
+            "raw": 18.5,
+            "fmt": "18.50"
+          },
+          "currentRatio": {
+            "raw": 1.21,
+            "fmt": "1.21"
+          },
+          "ebitda": {
+            "raw": 58500000000000,
+            "fmt": "58.50B"
+          },
+          "totalRevenue": {
+            "raw": 147900000000000,
+            "fmt": "147.90B"
+          }
+        },
+        "incomeStatementHistory": {}
+      }
+    ],
+    "error": null
+  }
+}