feat: extraction framework overhaul — extract_core shared package + SQLite state tracking

- Add extract/extract_core/ workspace package with three modules:
  - state.py: SQLite run tracking (open_state_db, start_run, end_run, get_last_cursor)
  - http.py: niquests session factory + etag normalization helpers
  - files.py: landing_path, content_hash, write_bytes_atomic (atomic gzip writes)
- State lives at {LANDING_DIR}/.state.sqlite — no extra env var needed
- SQLite chosen over DuckDB: state tracking is OLTP (row inserts/updates), not analytical
- Refactor all 4 extractors (psdonline, cftc_cot, coffee_prices, ice_stocks):
  - Replace inline boilerplate with extract_core helpers
  - Add start_run/end_run tracking to every extraction entry point
  - extract_cot_year returns int (bytes_written) instead of bool
- Update tests: assert result == 0 (not `is False`) for the return type change

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

uv.lock

@@ -11,6 +11,7 @@ members = [
     "beanflows",
     "cftc-cot",
     "coffee-prices",
+    "extract-core",
     "ice-stocks",
     "materia",
     "psdonline",
@@ -365,11 +366,15 @@ name = "cftc-cot"
 version = "0.1.0"
 source = { editable = "extract/cftc_cot" }
 dependencies = [
+    { name = "extract-core" },
     { name = "niquests" },
 ]
 
 [package.metadata]
-requires-dist = [{ name = "niquests", specifier = ">=3.14.1" }]
+requires-dist = [
+    { name = "extract-core", editable = "extract/extract_core" },
+    { name = "niquests", specifier = ">=3.14.1" },
+]
 
 [[package]]
 name = "charset-normalizer"
@@ -438,11 +443,15 @@ name = "coffee-prices"
 version = "0.1.0"
 source = { editable = "extract/coffee_prices" }
 dependencies = [
+    { name = "extract-core" },
     { name = "yfinance" },
 ]
 
 [package.metadata]
-requires-dist = [{ name = "yfinance", specifier = ">=0.2.55" }]
+requires-dist = [
+    { name = "extract-core", editable = "extract/extract_core" },
+    { name = "yfinance", specifier = ">=0.2.55" },
+]
 
 [[package]]
 name = "colorama"
@@ -740,6 +749,17 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/c1/ea/53f2148663b321f21b5a606bd5f191517cf40b7072c0497d3c92c4a13b1e/executing-2.2.1-py2.py3-none-any.whl", hash = "sha256:760643d3452b4d777d295bb167ccc74c64a81df23fb5e08eff250c425a4b2017", size = 28317, upload-time = "2025-09-01T09:48:08.5Z" },
 ]
 
+[[package]]
+name = "extract-core"
+version = "0.1.0"
+source = { editable = "extract/extract_core" }
+dependencies = [
+    { name = "niquests" },
+]
+
+[package.metadata]
+requires-dist = [{ name = "niquests", specifier = ">=3.14.1" }]
+
 [[package]]
 name = "fakeredis"
 version = "2.34.0"
@@ -1059,12 +1079,14 @@ name = "ice-stocks"
 version = "0.1.0"
 source = { editable = "extract/ice_stocks" }
 dependencies = [
+    { name = "extract-core" },
     { name = "niquests" },
     { name = "xlrd" },
 ]
 
 [package.metadata]
 requires-dist = [
+    { name = "extract-core", editable = "extract/extract_core" },
     { name = "niquests", specifier = ">=3.14.1" },
     { name = "xlrd", specifier = ">=2.0.1" },
 ]
@@ -2067,11 +2089,15 @@ name = "psdonline"
 version = "0.1.0"
 source = { editable = "extract/psdonline" }
 dependencies = [
+    { name = "extract-core" },
     { name = "niquests" },
 ]
 
 [package.metadata]
-requires-dist = [{ name = "niquests", specifier = ">=3.14.1" }]
+requires-dist = [
+    { name = "extract-core", editable = "extract/extract_core" },
+    { name = "niquests", specifier = ">=3.14.1" },
+]
 
 [[package]]
 name = "psutil"