fix+refactor: soft keywords as identifiers, full test wiring, ORC crash docs

- parser: clause keywords (header, format, status, user, csv, ...) now work
  as identifiers everywhere; IMPORT/EXPORT accept FORMAT csv/HEADER true
- nimble test + CI run all 13 test suites (650 checks green)
- ExecutionContext.registry is now {.cursor.} (breaks registry<->ctx cycle)
- ORC crash reproduced and bisected (tests/orc_repro.py); ARC stays the MM

tests/orc_repro.py

@@ -0,0 +1,57 @@
+#!/usr/bin/env python3
+"""Reproducer for the ORC cycle-collector crash (markGray/trace SIGSEGV).
+
+Usage:
+  1. Build the server with ORC:
+       nim c -d:ssl --threads:on --path:src --mm:orc -o:/tmp/baradadb_orc src/baradadb.nim
+  2. Start it:
+       BARADB_PORT=39472 BARADB_DATA_DIR=/tmp/baradb_orc_data BARADB_LOG_LEVEL=error /tmp/baradadb_orc
+  3. Run this script (from the repo root):
+       python3 tests/orc_repro.py
+
+Expected (as of 2026-07-30, Nim 2.2.10): the server dies with
+  orc.nim markGray -> trace -> SIGSEGV
+triggered from core/server.nim handleClient, and this script fails with
+ConnectionResetError. Under ARC (the default in nim.cfg) the same load passes.
+
+Bisect results: 200 pings + 200 SELECTs over TCP are fine; the crash lands
+somewhere between 20 and 500 sequential INSERTs (INSERT path only).
+Failed root-cause attempts: callback cycle breaks (ed5a719), {.cursor.} on
+ExecutionContext.registry (the registry<->ctx cycle), guarding ctx.onChange
+against zero WS subscribers. Conclusion: deep ORC+async issue (possibly
+upstream Nim), not a single app-level cycle. ARC remains the supported MM.
+"""
+
+import asyncio
+import sys
+
+sys.path.insert(0, "clients/python")
+from baradb import Client
+
+PORT = 39472
+
+
+async def worker(w: int) -> None:
+    base = 1000 + w * 100
+    async with Client("127.0.0.1", PORT) as c:
+        for i in range(100):
+            await c.query(f"INSERT INTO orc_stress (id, val) VALUES ({base + i}, 'v{base + i}')")
+
+
+async def main() -> None:
+    async with Client("127.0.0.1", PORT) as c:
+        await c.query("CREATE TABLE orc_stress (id INT PRIMARY KEY, val STRING)")
+        # Original report: SIGSEGV after ~20 sequential INSERTs under async load
+        for i in range(1000):
+            await c.query(f"INSERT INTO orc_stress (id, val) VALUES ({i}, 'x{i}')")
+        r = await c.query("SELECT COUNT(*) AS n FROM orc_stress")
+        print("after 1000 sequential INSERTs:", r.rows)
+    await asyncio.gather(*[worker(w) for w in range(10)])
+    async with Client("127.0.0.1", PORT) as c:
+        r = await c.query("SELECT COUNT(*) AS n FROM orc_stress")
+        print("final count:", r.rows)
+        print("ping:", await c.ping())
+    print("ORC STRESS OK")
+
+
+asyncio.run(main())